Frequency tuning of single photons from a whispering-gallery mode resonator to MHz-wide transitions - Schunk, G.; Vogl, Ulrich; Sedlmeir, F.; Strekalov, D. V.; Otterpohl, A.; Averchenko, V.; Schwefel, H. G. L.; Leuchs, Gerd; Marquardt, Christoph (Journal of Modern Optics, 2016)
Quantum repeaters rely on interfacing flying qubits with quantum memories. The most common implementations include a narrowband single photon matched in bandwidth and central frequency to an atomic system. Previously, we demonstrated the compatibility of our versatile source of heralded single photons, which is based on parametric down-conversion in a triply resonant whispering-gallery mode resonator, with alkaline transitions [Schunk et al., Optica 2015,2, 773]. In this paper, we analyse our source in terms of phase matching, available wavelength-tuning mechanisms and applications to narrowband atomic systems. We resonantly address the D1 transitions of caesium and rubidium with this optical parametric oscillator pumped above its oscillation threshold. Below threshold, the efficient coupling of single photons to atomic transitions heralded by single telecom-band photons is demonstrated. Finally, we present an accurate analytical description of our observations. Providing the demonstrated flexibility in connecting various atomic transitions with telecom wavelengths, we show a promising approach to realize an essential building block for quantum repeaters.
CRIS-Team Scopus Importer:2022-06-05
Keywords: (270.5565) Quantum communications; (300.6210) Spectroscopy; 190.4970 Parametric oscillators and amplifiers; atomic; OCIS: (270.0270) Quantum optics

From arrays of THz antennas to large-area emitters - Malzer, Stefan; Döhler, Gottfried; Garcia-Munoz, Enrique; Preu, Sascha; Bauerschmidt, Sebastian; Montero-De-Paz, J.; Ugarte-Munoz, E.; Rivera-Lavado, Alejandro; Segovia-Vargas, Daniel; Gonzalez-Posadas, V. (IEEE Transactions on Terahertz Science and Technology, 2013)
Arrays of coherently driven photomixers with antenna (antenna emitter arrays, AEAs) have been evaluated as a possibility to overcome the power limitations of individual conventional photomixers with antenna ('antenna emitters', AEs) for the generation of continuous-wave (CW) THz radiation. In this paper, 'large area emitters' (LAEs) are proposed as an alternative approach, and compared with AEAs. In this antenna-free new scheme of photomixing, the THz radiation originates directly from the acceleration of photo-induced charge carriers generated within a large semiconductor area. The quasi-continuous distribution of emitting elements corresponds to a high-density array and results in favorable radiation profiles without side lobes. Moreover, the achievable THz power is expected to outnumber even large AEAs. Last not least, the technological challenge of fabricating LAEs appears to be significantly less demanding. © 2011-2012 IEEE.

From third harmonic to triplet generation in micro structured fibers - Joly, Nicolas; Hammer, J.; Pennetta, Riccardo; Cavanna, A.; Jiang, Xin; Frosz, M. H.; Chekhova, Maria (2018 IEEE PHOTONICS CONFERENCE (IPC), 2018)
CRIS-Team WoS Importer:2019-03-20

Full-field characterization of helical Bloch modes guided in twisted coreless photonic crystal fiber - Roth, P.; Wong, G. K. L.; Frosz, M. H.; Ahmed, G.; Russell, Philip St. John (Optics Letters, 2019)
It was recently reported that a photonic crystal fiber (PCF) with no structural core guides light if a permanent chiral twist is introduced by spinning the fiber preform during the draw. The intriguing guidance mechanism behind this novel effect has many remarkable features; for example, it intrinsically supports circularly polarized helical Bloch modes (HBMs) that carry multiple optical vortices, making twisted PCFs of interest in fields such as optical micro-manipulation, imaging, quantum optics, and optical communications. Here we report for the first time, to the best of our knowledge, that a twisted coreless PCF supports not just one but a family of guided HBMs, each member of which has a unique transverse field distribution and harmonic spectrum. By making detailed interferometric measurements of the near-field phase and amplitude distributions of HBMs, and expanding them as a series of Bessel beams, we are able to extract the amplitude of each azimuthal and radial HBM harmonic. Good agreement is found with the numerical solutions of Maxwell's equations. The results shed light on the properties of this curious new optical phenomenon. (C) 2019 Optical Society of America
CRIS-Team WoS Importer:2019-10-25

Full-field mode sorter using two optimized phase transformations for high-dimensional quantum cryptography - Fickler, Robert; Bouchard, Frederic; Giese, Enno; Grillo, Vincenzo; Leuchs, Gerd; Karimi, Ebrahim (Journal of Optics, 2020)
High-dimensional encoding schemes have emerged as a novel way to perform quantum information tasks. For high dimensionality, temporal and transverse spatial modes of photons are the two paradigmatic degrees of freedom commonly used in such experiments. Nevertheless, general devices for multi-outcome measurements are still needed to take full advantage of the high-dimensional nature of encoding schemes. We propose a general full-field mode sorting scheme consisting of only up to two optimized phase elements based on evolutionary algorithms that allows for joint sorting of azimuthal and radial modes. We further study the performance of our scheme through simulations in the context of high-dimensional quantum cryptography, where sorting in different mutually unbiased bases and high-fidelity measurement schemes are crucial.
CRIS-Team WoS Importer:2020-01-31

Functional Plasmonic Nanocircuits with Low Insertion and Propagation Losses - Kriesch, Arian; Burgos, Stanley P.; Ploss, Daniel; Pfeifer, Hannes; Atwater, Harry A.; Peschel, Ulf (Nano Letters, 2013)
We experimentally demonstrate plasmonic nanocircuits operating as subdiffraction directional couplers optically excited with high efficiency from free-space using optical Yagi-Uda style antennas at extgreekl0 = 1550 nm. The optical Yagi-Uda style antennas are designed to feed channel plasmon waveguides with high efficiency (45% in coupling, 60% total emission), narrow angular directivity (<40°), and low insertion loss. SPP channel waveguides exhibit propagation lengths as large as 34 extgreekmm with adiabatically tuned confinement and are integrated with ultracompact (5 × 10 extgreekmm2), highly dispersive directional couplers, which enable 30 dB discrimination over extgreekDl = 200 nm with only 0.3 dB device loss.
EAM Import::2019-03-14

Fusion of computed tomography data and optical 3D images of the dentition for streak artefact correction in the simulation of orthognathic surgery - Nkenke, Emeka; Häusler, Gerd; Lell, Michael; et al. (Dentomaxillofacial Radiology, 2004)
Objective: To determine the limits of accuracy of fusion of optical three-dimensional (3D) imaging and computed tomography (CT) with and without metal artefacts in an experimental setting and to show the application of this hybrid system in 3D orthognathic surgery simulation. Methods: Ten plaster casts of dental arches were subjected to a CT scan and optical 3D surface imaging. Subsequently, the first molars in the plaster casts were supplied with metal restorations, bilaterally, and new CT scans and optical surface images were assessed. The registration of the surface data of the two imaging modalities of the study models without and with metal restorations was carried out. The mean distance between the two data sets was calculated. From a patient a CT scan of the skull as well as optical 3D images of plaster casts of the dental arches were acquired. Again the two imaging modalities were registered and virtual orthognathic surgery simulation was carried out. Results: The mean distance between the corresponding data points of CT and optical 3D surface images was 0.1262 ±0.0301 mm and 0.2671±0.0580 mm, respectively, for the plaster casts without and with metal restorations. The differences between these data were statistically significant (P< 0.0005). For the patient case a mean difference of 0.66±0.49 mm and 0.56±0.48 mm for mandible and maxilla, respectively, was calculated between CT and optical surface data. Conclusion: The accuracy of the fusion of 3D CT surface data and optical 3D imaging is significantly reduced by metal artefacts. However, it seems appropriate for virtual orthognathic surgery simulation, as post-operative orthodontics are performed frequently. © 2004 The British Institute of Radiology.
UnivIS-Import:2015-04-14:Pub.2004.nat.dphy.optik.1optik.fusion
Keywords: Computed tomography; Image fusion; Metal artefacts; Optical 3D imaging; Phase measuring triangulation

Gain enhancement by dielectric horns in the Terahertz band - Malzer, Stefan; Andres-Garcia, Belen; Garcia-Munoz, Enrique; Segovia-Vargas, Daniel; Bauerschmidt, Sebastian; Preu, Sascha; Döhler, Gottfried; Wang, Lijun (IEEE Transactions on Antennas and Propagation, 2011)
A new geometry for the design of antennas in the Terahertz band is presented. The structure is based on a horn antenna etched in the substrate and fed with a planar printed antenna used for generation of terahertz radiation, designed for the 200 GHz to 3 THz range. For the proposed antenna, the energy distribution through the substrate is reduced towards an increase in the gain of the system, at least, 8 dB in a 1:10 bandwidth. The structure has been measured showing the expected behavior in the low band. © 2006 IEEE.

GaN-Based Nanorods/Graphene Heterostructures for Optoelectronic Applications - Sarau, George; Heilmann, Martin; Latzel, Michael; Tessarek, Christian; Christiansen, Silke (physica status solidi (b), 2019)
The insulating character of sapphire, meltback etching of Si, bulk and surface defects prevented the efficient integration of GaN nanostructures in optoelectronic devices. Here, it is demonstrated that graphene can simultaneously serve as an electrical bottom contact, a chemically inert buffer layer, and a superior lattice and thermal matched growth substrate. Vertically aligned, high crystal quality GaN nanorods (NRs) without bulk defects such as threading dislocations and with only a mild strain at the NRs’ base are grown by metal-organic vapor-phase epitaxy on defect-free graphene using nanometer-sized Al x Ga 1−x N nucleation islands. Here no influence of the supporting substrate on the GaN epitaxy is observed. However, at defects in graphene the effects of dangling bonds and the underlying substrate, presumably through nanoholes in graphene, on the properties of GaN NRs are visible. It is also shown that surface defects in In x Ga 1−x N/GaN NRs from planar films produced by etching of the defective material can be effectively passivated with only 10 nm alumina deposited by atomic layer deposition. This is confirmed by the increase in electroluminescence measured on finished devices with graphene top contact. These results can potentially lead to new material combinations including graphene, GaN, and other relevant semiconductors like Si toward yet unexplored device concepts.
CRIS-Team Scopus Importer:2019-05-02
Keywords: defects; GaN; graphene; heterostructures; nanorods; nucleation; silicon

Gas-pressure tunable photon-pair generation in a suspended core fiber - Hammer, Jonas; Chekhova, Maria; Russell, Philip St. John; Joly, Nicolas (Frontiers in Optics - Proceedings Frontiers in Optics + Laser Science APS/DLS, 2019)
Four-wave-mixing in a suspended core fiber is spectrally tuned by filling the fiber with argon. This allows the generation of photon pairs to be tuned over at least 40 nm, extendible using even higher pressures.
CRIS-Team Scopus Importer:2021-04-20

Gaussian beam output from a large-mode-area higher-order-mode fiber - Lindlein, Norbert; et al. (2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, CLEO, 2007)

GAWBS noise reduction in microstructured fibers - Elser, Dominique Alexander; Korn, Alexander; Lorenz, Stefan; Glöckl, Oliver; Marquardt, Christoph; Andersen, Ulrik Lund; Leuchs, Gerd (2005 European Quantum Electronics Conference, EQEC '05, 2005)
Guided Acoustic Wave Brillouin Scattering (GAWBS) generates phase and polarization noise of light propagating in glass fibers. We experimentally demonstrate the reduction of GAWBS noise in microstructured fibers in comparison with standard fibers. © 2005 IEEE.
Created from Fastlane, Scopus look-up

Generalized Brillouin diagrams for evanescent waves in metamaterials with interelement coupling - Tatartschuk, Eugen; Radkovskaya, A.; Shamonina, E.; Solymar, L. (Physical Review B, 2010)
A graphical representation for two-dimensional periodic structures is introduced that provides the full information contained in the dispersion equation: not only for the pass band but for the neighboring stop bands as well. It is a seamless natural extension of Brillouin diagrams obtained by adding eight new zones which incorporate the properties of evanescent waves. The accuracy of the infinite lattice approximation is tested both by simulations and experiments using magnetoinductive waves. For waves propagating in one direction and evanescent in the other direction, the results of the three different methods are shown to be in good agreement. The versatility of the new representation and its applicability to the design of near-field manipulating metamaterials is discussed.
EAM Import::2019-03-13

Generalized theory of optical resonator and waveguide modes and their linear and Kerr nonlinear coupling - Silver, Jonathan M.; Del'Haye, Pascal (Physical Review A, 2022)
We derive a general theory of linear coupling and Kerr nonlinear coupling between modes of dielectric optical resonators from first principles. The treatment is not specific to a particular geometry or choice of mode basis, and can therefore be used as a foundation for describing any phenomenon resulting from any combination of linear coupling, scattering, and Kerr nonlinearity, such as bending and surface roughness losses, geometric backscattering, self- and cross-phase modulation, four-wave mixing, third-harmonic generation, and Kerr frequency comb generation. The theory is then applied to a translationally symmetric waveguide in order to calculate the evanescent coupling strength to the modes of a microresonator placed nearby, as well as the Kerr self- and cross-phase modulation terms between the modes of the resonator. This is then used to derive a dimensionless equation describing the symmetry-breaking dynamics of two counterpropagating modes of a loop resonator and prove that cross-phase modulation is exactly twice as strong as self-phase modulation only in the case that the two counterpropagating modes are otherwise identical.
CRIS-Team Scopus Importer:2022-03-18

Generation and applications of quantum engineered optical soliton pulses - Leuchs, Gerd; Andersen, Ulrik Lund; Glöckl, Oliver; Marquardt, Christoph; Heersink, Joel; Lorenz, Stefan (2005 European Quantum Electronics Conference, EQEC '05, 2005)
We describe various quantum protocols, all of which can be described by Bogoliubov transformations. Furthermore, a scheme by which correlated sidebands of a single spatial mode can be separated into two spatial modes is outlined. © 2005 IEEE.
Created from Fastlane, Scopus look-up

Generation and Direct Detection of Broadband Mesoscopic Polarization-Squeezed Vacuum - Leuchs, Gerd; et al. (Physical Review Letters, 2009)
Using a traveling-wave optical parametric amplifier with two orthogonally oriented type-I BBO crystals pumped by picosecond pulses, we generate vertically and horizontally polarized squeezed vacuum states within a broad frequency-angular range. Depending on the phase between these states, fluctuations in one or another Stokes parameter are suppressed below the shot-noise limit. Because of the large number of photon pairs produced, no local oscillator is required, and 3 dB squeezing is observed by means of direct detection. © 2009 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.optik.1optik.genera

Generation and Reconstruction of Two Mode Squeezed States in the Microwave Domain - Eichler, Christopher; et al. (APS March Meeting, 2011)
Keywords: wwwqudev

Generation and subwavelength focusing of longitudinal magnetic fields in a metallized fiber tip - Ploss, Daniel; Kriesch, Arian; Pfeifer, Hannes; Banzer, Peter; Peschel, Ulf (Optics Express, 2014)
We demonstrate experimentally and numerically that in fiber tips as they are used in NSOMs azimuthally polarized electrical fields (|Eazi|2 / |Etot|2 ≈55% ± 5% for extgreekl0= 1550 nm), respectively subwavelength confined (FWHM ≈450 nm ≈ extgreekl0/3.5) magnetic fields, are generated for a certain tip aperture diameter (d = 1.4 extgreekmm). We attribute the generation of this field distribution in metal-coated fiber tips to symmetry breaking in the bend and subsequent plasmonic mode filtering in the truncated conical taper.
EAM Import::2019-03-13

Generation of a radially polarized beam of high quality - Quabis, Susanne; Dorn, Ralf; Leuchs, Gerd (Applied Physics B-Lasers and Optics, 2005)
UnivIS-Import:2015-03-09:Pub.2005.nat.dphy.optik.1optik.genera

Generation of a wave packet tailored to efficient free space excitation of a single atom - Golla, Andrea; Chalopin, Benoit; Bader, Marianne; Harder, Irina; Mantel, Klaus; Maiwald, Robert; Lindlein, Norbert; Sondermann, Markus; Leuchs, Gerd (European Physical Journal D, 2012)
We demonstrate the generation of an optical dipole wave suitable for the process of efficiently coupling single quanta of light and matter in free space. We employ a parabolic mirror for the conversion of a transverse beam mode to a focused dipole wave and show the required spatial and temporal shaping of the mode incident onto the mirror. The results include a proof of principle correction of the parabolic mirror's aberrations. For the application of exciting an atom with a single photon pulse, we demonstrate the creation of a suitable temporal pulse envelope. We infer coupling strengths of 89% and success probabilities of up to 87% for the application of exciting a single atom for the current experimental parameters. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2012.

Generation of broad-band circularly polarised supercontinuum in chiral photonic crystal fibre - Sopalla, R.; Wong, G. K.L.; Joly, Nicolas; Jiang, X.; Frosz, M. H.; Ahmed, G.; Russell, Philip St. John (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Supercontinuum (SC) generation in solid-core photonic crystal fibres (PCFs) is well established and has diverse applications in science and technology [1,2]. In a conventional SC, the polarization state is not maintained over the whole spectrum due to cross-phase modulation and may in addition vary with power. Recently, it has been reported that continuously twisted PCFs exhibit circular birefringence [3,4]. Here we report the first experimental demonstration of a twisted PCF that robustly maintains circular polarization state across the whole spectrum, independent of power.
CRIS-Team Scopus Importer:2019-11-15

Generation of broadband circularly polarized supercontinuum light in twisted photonic crystal fibers - Sopalla, Rafal P.; Wong, Gordon K.L.; Joly, Nicolas; Frosz, Michael H.; Jiang, Xin; Ahmed, Goran; Russell, Philip St. John (Optics Letters, 2019)
We compare the properties of the broadband supercontinuum (SC) generated in twisted and untwisted solid-core photonic crystal fibers when pumped by circularly polarized 40 picosecond laser pulses at 1064 nm. In the helically twisted fiber, fabricated by spinning the preform during the draw, the SC is robustly circularly polarized across its entire spectrum whereas, in the straight fiber, axial fluctuations in linear birefringence and polarization-dependent nonlinear effects cause the polarization state to vary randomly with the wavelength. Theoretical modelling confirms the experimental results. Helically twisted photonic crystal fibers permit the generation of pure circularly polarized SC light with excellent polarization stability against fluctuations in input power and environmental perturbations.
CRIS-Team Scopus Importer:2019-08-23

Generation of continuous variable Einstein-Podolsky-Rosen entanglement via the Kerr nonlinearity in an optical fibre - Leuchs, Gerd; et al. (Physical Review Letters, 2001)
A report on generation of a continuous variable Einstein-Podolsky-Rosen (EPR) entanglement was presented using an optical fiber interferometer. Two independent squeezed beams were generated using Kerr nonlinearity. ERP entanglement was obtained between the output beams. Correlation of amplitude quadratures was measured below the quantum noise limit.
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.optik.1optik.genera

Generation of entangled matter qubits in two opposing parabolic mirrors - Trautmann, Nils; Bernad, Jozsef Zsolt; Sondermann, Markus; Alber, Gernot; Sanchez-Soto, Luis; Leuchs, Gerd (Physical Review A - Atomic, Molecular, and Optical Physics, 2014)
We propose a scheme for the remote preparation of entangled matter qubits in free space. For this purpose, a setup of two opposing parabolic mirrors is considered, each one with a single ion trapped at its focus. To get the required entanglement in this extreme multimode scenario, we take advantage of the spontaneous decay, which is usually considered as an apparent nuisance. Using semiclassical methods, we derive an efficient photon-path representation to deal with this problem. We also present a thorough examination of the experimental feasibility of the scheme. The vulnerabilities arising in realistic implementations reduce the success probability, but leave the fidelity of the generated state unaltered. Our proposal thus allows for the generation of high-fidelity entangled matter qubits with high rate.

Generation of N00N-like interferences with two thermal light sources - Bhatti, Daniel; Classen, Anton; Oppel, Steffen; Schneider, Raimund; von Zanthier, Joachim (European Physical Journal D, 2018)
Measuring the Mth-order intensity correlation function of light emitted by two statistically independent thermal light sources may display N00N-like interferences of arbitrary order N = Ma center dot 2. We show that via a particular choice of detector positions one can isolate M-photon quantum paths where either all M photons are emitted from the same source or Ma center dot 2 photons are collectively emitted by both sources. The latter superposition displays N00N-like oscillations with N = Ma center dot 2 which may serve, e.g., in astronomy, for imaging two distant thermal sources with Ma center dot 2-fold increased resolution. We also discuss slightly modified detection schemes improving the visibility of the N00N-like interference pattern and present measurements verifying the theoretical predictions.

Generation of non-classical light via selfinduced transparency in mercury-filled hollow core photonic crystal fibers - Vogl, Ulrich; Sedlmeir, Florian; Joly, Nicolas Y.; Marquardt, Christoph; Leuchs, Gerd; Marquardt, Christoph (Optics InfoBase Conference Papers, 2016)
We successfully demonstrate squeezing of nanosecond pulses via self-induced transparency in a system of mercury vapor confined in a hollow core kagomé-style fiber.
CRIS-Team Scopus Importer:2022-06-05

Generation of symmetric dicke states of remote qubits with linear optics - Thiel, Christoph; von Zanthier, Joachim; Bastin, Thierry; Solano, Enrique; Agarwal, Girish S. (Physical Review Letters, 2007)
We propose a method for generating all symmetric Dicke states, either in the long-lived internal levels of N massive particles or in the polarization degrees of freedom of photonic qubits, using linear optical tools only. By means of a suitable multiphoton detection technique, erasing Welcher-Weg information, our proposed scheme allows the generation and measurement of an important class of entangled multiqubit state

Generation of total angular momentum eigenstates in remote qubits - Maser, Andreas; Schilling, Uwe; Bastin, T.; Solano, E.; Thiel, Christoph; von Zanthier, Joachim (Physical Review A, 2009)
We propose a scheme enabling the universal coupling of angular momentum of N remote noninteracting qubits using linear optical tools only. Our system consists of N single-photon emitters in a Lambda configuration that are entangled among their long-lived ground-state qubits through suitably designed measurements of the emitted photons. In this manner, we present an experimentally feasible algorithm that is able to generate any of the 2(N) symmetric and nonsymmetric total angular momentum eigenstates spanning the Hilbert space of the N-qubit compoun
Keywords: eigenvalues and eigenfunctions; ground states; Hilbert spaces; quantum computing; quantum entanglement; quantum optics

Geometrical Optics - Lindlein, Norbert; Leuchs, Gerd (Handbook of Lasers and Optics, 2007)
UnivIS-Import:2015-04-20:Pub.2007.nat.dphy.optik.1optik.geomet

Geometric Spin Hall Effect of Light at polarizing interfaces - Korger, J.; Aiello, Andrea; Gabriel, C.; Banzer, Peter; Kolb, T.; Marquardt, Christoph; Leuchs, Gerd (Applied Physics B-Lasers and Optics, 2011)
The geometric Spin Hall Effect of Light (geometric SHEL) amounts to a polarization-dependent positional shift when a light beam is observed from a reference frame tilted with respect to its direction of propagation. Motivated by this intriguing phenomenon, the energy density of the light beam is decomposed into its Cartesian components in the tilted reference frame. This illustrates the occurrence of the characteristic shift and the significance of the effective response function of the detector. We introduce the concept of a tilted polarizing interface and provide a scheme for its experimental implementation. A light beam passing through such an interface undergoes a shift resembling the original geometric SHEL in a tilted reference frame. This displacement is generated at the polarizer and its occurrence does not depend on the properties of the detection system.We give explicit results for this novel type of geometric SHEL and show that at grazing incidence this effect amounts to a displacement of multiple wavelengths, a shift larger than the one introduced by Goos-Hänchen and Imbert-Fedorov effects. © 2011 Springer-Verlag.
CRIS-Team Scopus Importer:2022-06-05

Geometric spin Hall effect of light in tightly focused polarization-tailored light beams - Neugebauer, Martin; Banzer, Peter; Bauer, Thomas; Orlovas, Sergejus; Lindlein, Norbert; Aiello, Andrea; Leuchs, Gerd (Physical Review A - Atomic, Molecular, and Optical Physics, 2014)

GHz kinematic sensing with classically entangled beams of light - Berg-Johansen, Stefan; Töppel, Falk; Stiller, Birgit; Banzer, Peter; Ornigotti, M.; Giacobino, E.; Leuchs, Gerd; Aiello, Andrea; Marquardt, Christoph (Optics InfoBase Conference Papers, 2015)
CRIS-Team Scopus Importer:2021-06-29

Gold film-terminated 3-dimensional photonic crystals - Ding, B.; Pemble, M. E.; Korovin, A. V.; Peschel, Ulf; Romanov, Sergey (Applied Physics A-Materials Science & Processing, 2011)
Hybrid metal-dielectric photonic crystals assembled from an opal film coated by a gold film are designed in order to realize optical spectra that emanate from mixing Bloch modes in the opal and surface plasmon polaritons in corrugated gold films. The photonic crystal provides a spatial template for the gold film profile and modifies the electromagnetic vacuum in the vicinity to the gold layer. Reflectance spectroscopy was applied to deconvolute the plasmonic and photonic bandgap components in the optical response of hybrid crystals as opposite to their mixed appearance in the transmission spectra.
EAM Import::2019-03-13

Grain Dependent Growth of Bright Quantum Emitters in Hexagonal Boron Nitride - Mendelson, Noah; Morales-Inostroza, Luis; Li, Chi; Ritika, Ritika; Nguyen, Minh Anh Phan; Loyola-Echeverria, Jacqueline; Kim, Sejeong; Götzinger, Stephan; Toth, Milos; Aharonovich, Igor (Advanced Optical Materials, 2020)
Point defects in hexagonal boron nitride have emerged as a promising quantum light source due to their bright and photostable room temperature emission. In this work, the incorporation of quantum emitters during chemical vapor deposition growth on a nickel substrate is studied. Combining a range of characterization techniques, it is demonstrated that the incorporation of quantum emitters is limited to (001) oriented nickel grains. Such emitters display improved emission properties in terms of brightness and stability. These emitters are further utilized and integrated with a compact optical antenna enhancing light collection from the sources. The hybrid device yields average saturation count rates of approximate to 2.9 x 10(6) cps and an average photon purity of g((2))(0) approximate to 0.1. The results advance the understanding of single photon emitter incorporation during chemical vapor deposition growth and demonstrate a key step towards compact devices for achieving maximum collection efficiency.
CRIS-Team WoS Importer:2020-11-27

Graph Neural Networks for low-energy event classification & reconstruction in IceCube - Abbasi, R.; Ackermann, M.; Adams, J.; Aggarwal, N.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Alameddine, J. M.; Alves Jr, A. A.; Amin, N. M.; Andeen, K.; Anderson, T.; et al. (Journal of Instrumentation, 2022)
IceCube, a cubic-kilometer array of optical sensors built to detect atmospheric and astrophysical neutrinos between 1 GeV and 1 PeV, is deployed 1.45 km to 2.45 km below the surface of the ice sheet at the South Pole. The classification and reconstruction of events from the in-ice detectors play a central role in the analysis of data from IceCube. Reconstructing and classifying events is a challenge due to the irregular detector geometry, inhomogeneous scattering and absorption of light in the ice and, below 100 GeV, the relatively low number of signal photons produced per event. To address this challenge, it is possible to represent IceCube events as point cloud graphs and use a Graph Neural Network (GNN) as the classification and reconstruction method. The GNN is capable of distinguishing neutrino events from cosmic-ray backgrounds, classifying different neutrino event types, and reconstructing the deposited energy, direction and interaction vertex. Based on simulation, we provide a comparison in the 1 GeV-100 GeV energy range to the current state-of-the-art maximum likelihood techniques used in current IceCube analyses, including the effects of known systematic uncertainties. For neutrino event classification, the GNN increases the signal efficiency by 18% at a fixed background rate, compared to current IceCube methods. Alternatively, the GNN offers a reduction of the background (i.e. false positive) rate by over a factor 8 (to below half a percent) at a fixed signal efficiency. For the reconstruction of energy, direction, and interaction vertex, the resolution improves by an average of 13%-20% compared to current maximum likelihood techniques in the energy range of 1 GeV-30 GeV. The GNN, when run on a GPU, is capable of processing IceCube events at a rate nearly double of the median IceCube trigger rate of 2.7 kHz, which opens the possibility of using low energy neutrinos in online searches for transient events.
CRIS-Team WoS Importer:2023-02-17

Gravitational radiation from birefringent matter dynamics - Alex, Nils (Physical Review D, 2020)
We present the second-order gravitational dynamics for a spacetime inhabited by matter fields which feature vacuum birefringence. The derivation follows a perturbative variant of the covariant constructive gravity program, ensuring diffeomorphism invariance of gravity and causal compatibility of matter theory and gravity. A subsequent spatiotemporal split of this theory reveals the presence of unphysical artifacts, which are cured by imposing constraints on the gravitational constants, reducing their number from ten to seven. Within this sector, we derive the gravitational radiation emitted by a binary system in circular motion. The system emits massless waves, which correspond to the radiation predicted by Einstein gravity, but also massive waves, which are generated only above a certain angular frequency threshold and are unknown to Einstein gravity. A gravitational-wave detector modeled as a sphere of freely falling test masses shows quantitatively and qualitatively new behavior under the influence of this radiation. The result is a prediction of gravitational self-coupling from first principles, demonstrating the predictive power of covariant constructive gravity for modified gravity research, especially in the era of gravitational-wave astronomy.
CRIS-Team WoS Importer:2020-11-27

Grazing incidence interferometry for rough convex aspherics - Schwider, Johannes; Kellermann, Christine; Lindlein, Norbert; Rothau, Sergej; Mantel, Klaus (arXiv, 2016)

Grazing incidence interferometry for testing rough asperics - Rothau, Sergej; Schwider, Johannes; Mantel, Klaus; Lindlein, Norbert (Optical Measurement Systems for Industrial Inspection XI, 2019)
Keywords: interferometry; grazing incidence; rough aspherics; phase shifting; surface measurement

Grazing incidence interferometry for testing rough aspherics: experimental results and data analysis - Rothau, Sergey; Mantel, K.; Lindlein, Norbert (OPTICS AND PHOTONICS FOR ADVANCED DIMENSIONAL METROLOGY, 2021)
CRIS-Team WoS Importer:2021-07-30

Grazing incidence test for cylindrical microlenses with high numerical aperture - Lindlein, Norbert; et al. (Journal of Optics A-Pure and Applied Optics, 2002)
Cylinder symmetry of test objects allows grazing incidence tests. Here we propose the use of two diffractive optical elements (DOEs) instead of a single DOE in perpendicular incidence. The splitting of the optical function of the DOEs allows low spatial frequencies in the diffractive elements. In fact, the diffractive structures are curves parallel to the meridian of the cylinder lens. Here an interferometric test is described where identical DOEs serve as beamsplitter and combiner. The undiffracted wavefront serves as reference. Phase shifting evaluations are possible by axial translations of one of the DOEs. The effective wavelength can be chosen within wide limits. Actually, we used a pitch of 5 μm, which is identical to the effective wavelength of the test. A surface deviation of 2.5 μm corresponds to a fringe distance. The interferometric test enables rms values of better than 20 nm for any aspheric geometry of the meridian curve, even with lenses having numerical apertures up to 0.9.
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.grazin
Keywords: Computer-generated holograms; Interferometers; Phase shifting interferometry

Growth of GaN micro- and nanorods on graphene-covered sapphire: Enabling conductivity to semiconductor nanostructures on insulating substrates - Heilmann, Martin; Sarau, George; Göbelt, Manuela; Latzel, Michael; Sadhujan, Sumesh; Tessarek, Christian; Christiansen, Silke (Crystal Growth and Design, 2015)
The self-catalyzed growth of vertically aligned and hexagonally shaped GaN micro- and nanorods on graphene transferred onto sapphire is achieved through metal-organic vapor phase epitaxy. However, a great influence of the underlying substrate is evident, since vertically aligned structures with a regular shape could not be grown on graphene transferred to SiO2. The optical properties of the regular GaN nanorods were investigated by spatially and spectrally resolved cathodoluminescence showing defect related emission only near the interface between the sapphire substrate and nanorods but not from their upper part. Micro-raman spectroscopy confirms that the single-layer graphene remains virtually unchanged in terms of the Raman signal, even after undergoing high temperatures (∼1200 °C) during nanorod growth. Furthermore, Raman mapping demonstrates that GaN structures predominantly grow on defective parts of graphene, giving new insight into the nucleation and growth mechanism of semiconductors on graphene. To validate the conductivity of graphene, when being attached to the sapphire substrate and after the nanorod growth, current-voltage investigations were carried out on single, as-grown, GaN nanorods with a nanoprober in a scanning electron microscope. These measurements demonstrate the viability of graphene as a conductive electrode, for example, as a back contact for GaN nanorods grown on insulating sapphire.

Guided acoustic wave Brillouin scattering in photonic crystal fibers - Elser, Dominique Alexander; Wittmann, Christoffer; Andersen, Ulrik Lund; Glöckl, Oliver; Lorenz, Stefan; Marquardt, Christoph; Leuchs, Gerd (Journal of Physics: Conference Series, 2007)
In silica glass fibers, thermally excited acoustic phonons scatter light into the beam propagating in the forward direction. At acoustic frequencies up to several hundreds of megahertz, the wave vectors of the phonons interacting with the light propagate essentially transversally to the fiber axis. This effect is known as Guided Acoustic Wave Brillouin Scattering (GAWBS) and leads to phase and polarization noise in the guided light. For fiber-based quantum optics experiments, this excess noise is a major limitation. In Photonic Crystal Fibers (PCFs), light is guided by a microstructure simultaneously acting as a 2D transversal phononic crystal which modifies the acoustic noise spectrum. We demonstrate a GAWBS-noise reduction in commercially available PCFs. This gives rise to the prospect of fiber-based quantum optic devices exhibiting less excess noise, thus resulting in higher quantum state purity. Further improvement can be achieved by tailoring the photonic microstructure such that a reduction of phonon noise by design is achieved. © 2007 IOP Publishing Ltd.
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Helstrom measurement: A nondestructive implementation - Han, Rui; Leuchs, Gerd; Bergou, Janos A. (Physical Review A, 2020)
We discuss an implementation of the minimum error state discrimination measurement, originally introduced by Helstrom [Quantum Detection and Estimation Theory (Academic Press, New York, 1976)]. In this implementation, instead of performing the optimal projective measurement directly on the system, it is first entangled to an ancillary system and the measurement is performed on the ancilla. We show that, by an appropriate choice of the entanglement transformation, the Helstrom bound can be attained. The advantage of this approach is twofold. First, it provides an implementation when the optimal projective measurement cannot be directly performed. For example, in the case of continuous variable states (binary and N phase-shifted coherent signals), the available detection methods, photon counting and homodyning, are insufficient to perform the required cat-state projection. In the case of symmetric states, the square-root measurement is optimal, but it is not easy to perform directly for more than two states. Our approach provides a feasible alternative in both cases. Second, the measurement is nondestructive from the point of view of the original system and one has a certain amount of freedom in designing the post-measurement state, which can then be processed further.
CRIS-Team WoS Importer:2020-03-24

Heralded entanglement of arbitrary degree in remote qubits - Schilling, Uwe; Thiel, Christoph; Solano, E.; Bastin, T.; von Zanthier, Joachim (Physical Review A, 2009)
Incoherent scattering of photons off two remote atoms with a Lambda-level structure is used as a basic Young-type interferometer to herald long-lived entanglement of an arbitrary degree. The degree of entanglement, as measured by the concurrence, is found to be tunable by two easily accessible experimental parameters. Fixing one of them to certain values unveils an analog to the Malus' law. An estimate of the variation in the degree of entanglement due to uncertainties in an experimental realization is give

Hertel exophtalmometry versus computed tomography and optical 3D imaging for the determination of the globe position in zygomatic fractures - Häusler, Gerd; Nkenke, Emeka; Neukam, Friedrich Wilhelm; et al. (International Journal of Oral and Maxillofacial Surgery, 2004)
UnivIS-Import:2015-03-09:Pub.2004.nat.dphy.optik.1optik.hertel

Hierarchical quantum master equation approach to charge transport in molecular junctions with time-dependent molecule-lead coupling strengths - Erpenbeck, André; Götzendörfer, Lukas; Schinabeck, Christian; Thoss, Michael (European Physical Journal - Special Topics, 2019)
Time-dependent currents in molecular junctions can be caused by structural fluctuations or interaction with external fields. In this paper, we demonstrate how the hierarchical quantum master equation approach can be used to study time-dependent transport in a molecular junction. This reduced density matrix methodology provides a numerically exact solution to the transport problem including time-dependent energy levels, molecule-lead coupling strengths and transitions between electronic states of the molecular bridge. Based on a representative model, the influence of a time-dependent molecule-lead coupling on the electronic current is analyzed in some detail.
CRIS-Team WoS Importer:2019-04-12

High-dimensional intracity quantum cryptography with structured photons - Sit, Alicia; Bouchard, Frederic; Fickler, Robert; Gagnon-Bischoff, Jeremie; Larocque, Hugo; Heshami, Khabat; Elser, Dominique; Peuntinger, Christian; Günthner, Kevin; Heim, Bettina; Marquardt, Christoph; Leuchs, Gerd; et al. (Optica, 2017)
Quantum key distribution (QKD) promises information-theoretically secure communication and is already on the verge of commercialization. The next step will be to implement high-dimensional protocols in order to improve noise resistance and increase the data rate. Hitherto, no experimental verification of high-dimensional QKD in the single-photon regime has been conducted outside of the laboratory. Here, we report the realization of such a single-photon QKD system in a turbulent free-space link of 0.3 km over the city of Ottawa, taking advantage of both the spin and orbital angular momentum photonic degrees of freedom. This combination of optical angular momenta allows us to create a 4-dimensional quantum state; wherein, using a high-dimensional BB84 protocol, a quantum bit error rate of 11% was attained with a corresponding secret key rate of 0.65 bits per sifted photon. In comparison, an error rate of 5% with a secret key rate of 0.43 bits per sifted photon is achieved for the case of 2-dimensional structured photons. We thus demonstrate that, even through moderate turbulence without active wavefront correction, high-dimensional photon states are advantageous for securely transmitting more information. This opens the way for intracity high-dimensional quantum communications under realistic conditions.
CRIS-Team Scopus Importer:2022-06-05
Keywords: Free-space optical communication; Optical vortices; Quantum cryptography

High index-contrast all-solid photonic crystal fibers by pressure-assisted melt infiltration of silica matrices - Da, Ning; Wondraczek, Lothar; Schmidt, Markus A.; Granzow, Nicolai; Russell, Philip St. John (Journal of Non-Crystalline Solids, 2010)
All-solid photonic crystal fibers (PCFs) are created by pressure-assisted filling of low-melting-point chalcogenide and tellurite glasses into silica matrix fibers with channel diameters as small as 200 nm. Overcoming to a large extent the problem of viscosity and, thus, process incompatibility of silica and non-silicate optical glasses, the technique provides a unique way of producing waveguiding devices with high core-cladding index-contrast, high optical non-linearity and a transmission range that extends into the mid infrared. In this paper, as a prerequisite for waveguide production, the rheologic properties and controlled flow of highly-viscous liquids under geometrically confined conditions are considered, and deviations from Newtonian behavior are discussed. Because the filling process requires only very small quantities of filling material that do not come into contact with the environment, and because ultra-high cooling rates can be achieved, the technique enables the use of difficult-to-handle or reactive optical glasses.
EAM Import::2019-03-13

Highly efficient deep UV generation by four-wave mixing in gas-filled hollow-core photonic crystal fiber - Belli, Federico; Abdolvand, Amir; Travers, John C.; Russell, Philip St. John (Optics Letters, 2019)
We report on a highly efficient experimental scheme for the generation of deep-ultraviolet (UV) ultrashort light pulses using four-wave mixing in gas-filled kagomé-style photonic crystal fiber. By pumping with ultrashort, few microjoule pulses centered at 400 nm, we generate an idler pulse at 266 nm and amplify a seeded signal at 800 nm. We achieve remarkably high pump-to-idler energy conversion efficiencies of up to 38%. Although the pump and seed pulse durations are ∼100 fs, the generated UV spectral bandwidths support sub-15 fs pulses. These can be further extended to support few-cycle pulses. Four-wave mixing in gas-filled hollow-core fibers can be scaled to high average powers and different spectral regions such as the vacuum UV (100–200 nm).
CRIS-Team Scopus Importer:2019-12-03

Highly efficient generation of narrow-band single-mode photon pairs from a whispering gallery mode resonator - Förtsch, Michael; Schunk, Gerhard; Josef Fürst,; Strekalov, Dmitry; Gerrits, Thomas; Stevens J., Martin J.; Sedlmeir, Florian; Schwefel G.L., Harald G.L.; Nam, Sae Woo; Leuchs, Gerd; Marquardt, Christoph (Optics InfoBase Conference Papers, 2014)
We present a highly efficient narrow-band pair-photon source based on a crystalline whispering gallery mode resonator, which emits photons in exactly one spatiotemporal mode. © 2014 Optical Society of America.
CRIS-Team Scopus Importer:2022-06-05

Highly efficient generation of single-mode photon pairs from a crystalline whispering-gallery-mode resonator source - Foertsch, Michael; Schunk, Gerhard; Fuerst, Josef U.; Strekalov, Dmitry; Gerrits, Thomas; Stevens, Martin J.; Sedlmeir, Florian; Schwefel, Harald G. L.; Nam, Sae Woo; Leuchs, Gerd; Marquardt, Christoph (Physical Review A - Atomic, Molecular, and Optical Physics, 2015)
We report a highly efficient source of narrow-band photon pairs based on parametric down-conversion in a crystalline whispering-gallery-mode resonator. Remarkably, each photon of a pair is detected in a single spatial and temporal mode, as witnessed by Glauber's autocorrelation function. We explore the phase-matching conditions in spherical geometries, and determine the requirements for single-mode operation. Understanding these conditions has allowed us to experimentally demonstrate a single-mode pair-detection efficiency of 1.13×106 pairs/s per mW pump power per 26.8 MHz bandwidth.
CRIS-Team Scopus Importer:2022-06-05

Highly improved range sensing - by reduction of spatial coherence - Häusler, Gerd; et al. (Optik, 2001)
Optical range sensors based on triangulation are widely used for the shape measurement of optically rough objects. The origin of the achievable measuring uncertainty of the distance is speckle noise. Speckle noise is unavoidable in spatially coherent systems. We demonstrate two experiments which prove that without spatial coherence, the measuring uncertainty can be dramatically reduced, and we present an on-line 3D-sensor for laser-material processing, exploiting this knowledge.
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.optik.1optik.highly
Keywords: Coherent noise; Distance measurement; Laser material processing; Optical metrology; Triangulation

High numerical aperture imaging with different polarization patterns - Lindlein, Norbert; Quabis, Susanne; Peschel, Ulf; Leuchs, Gerd (Optics Express, 2007)
The modulation transfer function (MTF) is calculated for imaging with linearly, circularly and radially polarized light as well as for different numerical apertures and aperture shapes. Special detectors are only sensitive to one component of the electric energy density, e.g. the longitudinal component. For certain parameters this has advantages concerning the resolution when comparing to polarization insensitive detectors. It is also shown that in the latter case zeros of the MTF may appear which are purely due to polarization effects and which depend on the aperture angle. Finally some ideas are presented how to use these results for improving the resolution in lithography. © 2007 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2007.nat.dphy.optik.1optik.highnu

High power terahertz photomixer arrays - Andres-Garcia, Belen; Garcia-Munoz, Enrique; Segovia-Vargas, Daniel; Bauerschmidt, Sebastian; Döhler, Gottfried; Preu, Sascha; Malzer, Stefan; Lu, Hong; Gossard, Art (6th European Conference on Antennas and Propagation, EuCAP 2012, 2012)
Two solutions for high power terahertz radiation are discussed in this paper. The first solution is based on classical array theory, presenting an array of 55 elements, where we achieve upon combining the beams an increased directivity of 18 dB in comparison with the 8 dB of an isolated antenna. Measurements for the different elements of the array are presented. The second solution is the use of large area emitters, where the larger area allows a higher illumination power having a higher radiated power. © 2012 IEEE.

High-Precision Localization of Trapped Microparticles inside Hollow-Core Photonic Crystal Fibers using Coherent Optical Frequency Domain Reflectometry - Köppel, Max; Sharma, Abhinav; Renner, Esther; Xie, Shangran; Schmauß, Bernhard; Russell, P. St J. (2019 IEEE SENSORS, 2020)
We present a localization technique for an optically trapped microparticle inside hollow-core photonic crystal fibers which is the basis of a new generation of fiber optical sensors. A polystyrene particle of diameter 15 µm is optically trapped and moved inside the hollow-core fiber by optical forces while its position is tracked using coherent optical frequency domain reflectometry. We demonstrate that this technique can locate the particle position with a standard deviation of 10 µm. By applying a time-apertured Fourier transform, the dynamics of particle motion can be resolved with millisecond temporal resolutio

High-Precision Protein-Tracking With Interferometric Scattering Microscopy - Taylor, Richard W.; Holler, Cornelia; Mahmoodabadi, Reza Gholami; Küppers, Michelle; Mirzaalian Dastjerdi, Houman; Zaburdaev, Vasily; Schambony, Alexandra; Sandoghdar, Vahid (Frontiers in Cell and Developmental Biology, 2020)
The mobility of proteins and lipids within the cell, sculpted oftentimes by the organization of the membrane, reveals a great wealth of information on the function and interaction of these molecules as well as the membrane itself. Single particle tracking has proven to be a vital tool to study the mobility of individual molecules and unravel details of their behavior. Interferometric scattering (iSCAT) microscopy is an emerging technique well-suited for visualizing the diffusion of gold nanoparticle-labeled membrane proteins to a spatial and temporal resolution beyond the means of traditional fluorescent labels. We discuss the applicability of interferometric single particle tracking (iSPT) microscopy to investigate the minutia in the motion of a protein through measurements visualizing the mobility of the epidermal growth factor receptor in various biological scenarios on the live cell.
CRIS-Team Scopus Importer:2020-11-27
Keywords: epidermal growth factor receptor; interferometric scattering microscopy; iSCAT; iSPT; live cell imaging; membrane organization; single particle tracking

High-quality 8-fold self-compression of ultrashort near-UV pulses in an Ar-filled ultrathin-walled photonic crystal fiber - Luan, Jie; Russell, Philip St. J.; Novoa, David (Photonics Research, 2022)
We demonstrate generation of 7.6 fs near-UV pulses centered at 400 nm via 8-fold soliton-effect self-compression in an Ar-filled hollow-core kagome-style photonic crystal fiber with ultrathin core walls. Analytical calculations of the effective compression length and soliton order permit adjustment of the experimental parameters, and numerical modeling of the nonlinear pulse dynamics in the fiber accurately predicts the spectrotemporal profiles of the self-compressed pulses. After compensation of phase distortion introduced by the optical elements along the beam path from the fiber to the diagnostics, 71% of the pulse energy was in the main temporal lobe, with peak powers in excess of 0.2 GW. The convenient setup opens up new opportunities for time-resolved studies in spectroscopy, chemistry, and materials science. (c) 2022 Chinese Laser Press
CRIS-Team WoS Importer:2022-12-09

High resolution position measurement of “flying particles” inside hollow-core photonic crystal fiber - Werzinger, Stefan; Bykov, Dmitry S.; Zeltner, Richard; Machnev, Andrey; Köppel, Max; Xie, Shangran; Schmauß, Bernhard; Russell, Philip St. John (IEEE Sensors Conference, 2017)
Optically trapped “flying particles” inside hollow core photonic crystal fiber (HC-PCF) can be used as multiparameter sensors of, for example, temperature, radiation levels or external electric fields. They represent a new type of optical fiber sensor, offering a spatial resolution that is only limited by the particle size, while being functionally reconfigurable. Here we demonstrate accurate measurement of the axial position of flying particles using incoherent optical frequency domain reflectometry in combination with model-based estimation processing. The approach allows to measure the particle position inside the HC-PCF with a precision of 140 μ

High-resolution, three-dimensional investigation of protein diffusion and trafficking in the live HeLa cell via interferometrie scattering microscopy (iSCAT) - Taylor, Richard; Mahmoodabadi, Reza Gholami; Schambony, Alexandra; Sandoghdar, Vahid (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Transmembrane proteins exhibit a wide variety of mobility in live cells, including diffusion in the plasma membrane and directed transport into the cell via endocytosis. Although a great deal has been uncovered about the biochemistry underlying these processes, their real-time visualisation in situ with the necessary nanoscopic resolution remains a daunting experimental challenge. Conventional microscopies rely on fluorescent labelling to monitor diffusion of such proteins within live cells. The resolution in both space and time by which one can successfully determine the position of the protein is curtailed by the finite and limited emission rate of the fluorophore.
CRIS-Team Scopus Importer:2019-11-15

Holographic Measurement of Surface Topography - Limits and New Options - Häusler, Gerd; Willomitzer, Florian (DGsO-Proceedings 2023, 2023)
There is a plethora of options for optical 3D-metrology. Inspired by the progress of digital holography, we discuss two questions: Can we implement all classical (non-holographic) sensors via digital holography? And even more interesting: Can digital holography enable options beyond classical sensors?
Keywords: holography; metrology; topography; 3-D

Holographic microlens arrays - Lindlein, Norbert; et al. (EOS Topical Meetings Digest Series, 1995)
UnivIS-Import:2015-03-05:Pub.1995.nat.dphy.optik.1optik.hologr

Homogenization and beam shaping with micro lens arrays - Harder, Irina; Lano, Maik; Lindlein, Norbert; Schwider, Johannes (Proceedings of SPIE, 2004)
UnivIS-Import:2015-04-14:Pub.2004.nat.dphy.optik.1optik.homoge

Homogenization and beam shaping with microlens arrays - Lindlein, Norbert; et al. (Photon Management, 2004)
Mostly, the typical light distribution of a light source, as a LED or an excimer laser, is not suitable for the application. The excimer laser beam for example shows a distinct elliptical Gaussian profile. As another example the layout of the light emitting chip and the reflector of a LED form an extremely inhomogeneous luminescent area. To achieve a better adapted beam profile a homogenizing setup with beam shaping qualities can be used. In this talk two setups for homogenization with the help of refractive micro lens arrays are shown and compared. The main attention is turned on the influence of the numerical aperture of the micro lenses, the limitations due to the spatial coherence degree and the difficulties of the alignment of the systems. In addition, a diffractive solution of homogenization for spatial partially coherence is presented.
Keywords: Beam shaping; Excimer; Homogenization; LED; Microlens array; Spatial coherence

How much 3D-Information can weacquire? Optical Range Sensors at the Physical Limit, and where to apply them - Häusler, Gerd (Proceedings of Third International Conference on 3-DDigital Imaging and Modeling, 2001)
UnivIS-Import:2015-04-16:Pub.2001.nat.dphy.optik.1optik.howmuc

How much should we pay for optical 3d-sensors? - a respectable scientific question - Häusler, Gerd (Proceedings of ICO 04, Tokyo, 2004)
UnivIS-Import:2015-03-09:Pub.2004.nat.dphy.optik.1optik.howmuc

Huygens' dipole for polarization-controlled nanoscale light routing - Nechayev, Sergey; Eismann, Jörg; Neugebauer, Martin; Wozniak, Pawel; Bag, Ankan; Leuchs, Gerd; Banzer, Peter (Physical Review A, 2019)
Structured illumination allows for satisfying the first Kerker condition of in-phase perpendicular electric and magnetic dipole moments in any isotropic scatterer that supports electric and magnetic dipole resonances. The induced Huygens' dipole may be utilized for unidirectional coupling to waveguide modes that propagate transverse to the excitation beam. We study two configurations of a Huygens' dipole, longitudinal electric and transverse magnetic dipole moments or vice versa. We experimentally show that only the radially polarized emission of the first and azimuthally polarized emission of the second configuration are directional in the far field. This polarization selectivity implies that directional excitation of either transverse magnetic (TM) or transverse electric (TE) waveguide modes is possible. Applying this concept to a single dielectric nanoantenna excited with structured light, we are able to experimentally achieve scattering directivities of around 23 and 18 dB in TM and TE modes, respectively. This strong directivity paves the way for tunable polarization-controlled nanoscale light routing and applications in optical metrology, localization microscopy, and on-chip optical devices.
CRIS-Team WoS Importer:2019-04-30

Hybrid Colloidal Plasmonic-Photonic Crystals - Romanov, Sergei G.; Korovin, Alexander V.; Regensburger, Alois; Peschel, Ulf (Advanced Materials, 2011)
We review the recently emerged class of hybrid metal-dielectric colloidal photonic crystals. The hybrid approach is understood as the combination of a dielectric photonic crystal with a continuous metal film. It allows to achieve a strong modification of the optical properties of photonic crystals by involving the light scattering at electronic excitations in the metal component into moulding of the light flow in series to the diffraction resonances occurring in the body of the photonic crystal. We consider different realizations of hybrid plasmonic-photonic crystals based on two- and three-dimensional colloidal photonic crystals in association with flat and corrugated metal films. In agreement with model calculations, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tuneable functionality of these crystals.
EAM Import::2019-03-13

Hybrid Metal-Dielectric Photonic Crystals with Enhanced Plasmonic-Photonic Interaction - Bahrami, M. Reza; Lobaz, Volodymyr; Peukert, Wolfgang; Korovin, Alexander V.; Peschel, Ulf; Romanov, Sergei G. (13th International Conference on Transparent Optical Networks (ICTON), 2011)
Control on the optical response of 2-dimensional colloidal photonic crystals was achieved by combining them with thin metal films. In such hybrids the light transport depends on the parameters of the sphere lattice and the topology of the metal film. This approach allows mixing Bloch modes and surface plasmon polariton modes in the total optical response of hybrid architectures. Stronger modification of the hybrid's optical properties was achieved in the case of tighter light confinement.
Keywords: hybrid photonic crystal; surface plasmon polariton; optical transmission

Hybrid Orthorhombic Carbon Flakes Intercalated with Bimetallic Au-Ag Nanoclusters: Influence of Synthesis Parameters on Optical Properties - Butt, Muhammad Abdullah; Mamonova, Daria; Petrov, Yuri; Proklova, Alexandra; Kritchenkov, Ilya; Manshina, Alina; Banzer, Peter; Leuchs, Gerd (Nanomaterials, 2020)
Until recently, planar carbonaceous structures such as graphene did not show any birefringence under normal incidence. In contrast, a recently reported novel orthorhombic carbonaceous structure with metal nanoparticle inclusions does show intrinsic birefringence, outperforming other natural orthorhombic crystalline materials. These flake-like structures self-assemble during a laser-induced growth process. In this article, we explore the potential of this novel material and the design freedom during production. We study in particular the dependence of the optical and geometrical properties of these hybrid carbon-metal flakes on the fabrication parameters. The influence of the laser irradiation time, concentration of the supramolecular complex in the solution, and an external electric field applied during the growth process are investigated. In all cases, the self-assembled metamaterial exhibits a strong linear birefringence in the visible spectral range, while the wavelength-dependent attenuation was found to hinge on the concentration of the supramolecular complex in the solution. By varying the fabrication parameters one can steer the shape and size of the flakes. This study provides a route towards fabrication of novel hybrid carbon-metal flakes with tailored optical and geometrical properties.
CRIS-Team WoS Importer:2020-08-14

Idealized Einstein-Podolsky-Rosen states from non-phase-matched parametric down-conversion - Okoth, Cameron; Kovlakov, E.; Boensel, F.; Cavanna, A.; Straupe, S.; Kulik, S. P.; Chekhova, Maria (Physical Review A, 2020)
The most common source of entangled photons is spontaneous parametric down-conversion (SPDC). The degree of energy and momentum entanglement in SPDC is determined by the nonlinear interaction volume. By reducing the length of a highly nonlinear material, we relax the longitudinal phase-matching condition and reach record levels of transverse momentum entanglement. The degree of entanglement is estimated using both correlation measurements and stimulated emission tomography in wave-vector space. The high entanglement of the state in wave-vector space can be used to massively increase the quantum information capacity of photons, but more interestingly the equivalent state measured in position space is correlated over distances far less than the photon wavelength. This property promises to improve the resolution of many quantum imaging techniques beyond the current state of the art.
CRIS-Team WoS Importer:2020-02-04

Identifying modes of large whispering-gallery mode resonators from the spectrum and emission pattern - Schunk, Gerhard; Fuerst, Josef U.; Foertsch, Michael; Strekalov, Dmitry V.; Vogl, Ulrich; Sedlmeir, Florian; Schwefel, Harald G. L.; Leuchs, Gerd; Marquardt, Christoph (Optics Express, 2014)
Identifying the mode numbers in whispering-gallery mode resonators (WGMRs) is important for tailoring them to experimental needs. Here we report on a novel experimental mode analysis technique based on the combination of frequency analysis and far-field imaging for high mode numbers of large WGMRs. The radial mode numbers q and the angular mode numbers p = l-m are identified and labeled via far-field imaging. The polar mode numbers l are determined unambiguously by fitting the frequency differences between individual whispering gallery modes (WGMs). This allows for the accurate determination of the geometry and the refractive index at different temperatures of the WGMR. For future applications in classical and quantum optics, this mode analysis enables one to control the narrow-band phase-matching conditions in nonlinear processes such as second-harmonic generation or parametric down-conversion.
CRIS-Team Scopus Importer:2022-06-05

Imaging individual barium atoms in solid xenon for barium tagging in nEXO - Chambers, C.; Walton, T.; Fairbank, D.; Craycraft, A.; Yahne, D. R.; Todd, J.; Iverson, A.; Fairbank, W.; Alamre, A.; Albert, J. B.; Anton, Gisela; Arnquist, I. J.; et al. (Nature, 2019)
Double-β-decay involves the simultaneous conversion of two neutrons into two protons, and the emission of two electrons and two neutrinos; the neutrinoless process, although not yet observed, is thought to involve the emission of the two electrons but no neutrinos. The search for neutrinoless-double-β-decay probes fundamental properties of neutrinos, including whether or not the neutrino and antineutrino are distinct particles. Double-β-decay detectors are large and expensive, so it is essential to achieve the highest possible sensitivity with each study, and removing spurious contributions (‘background’) from detected signals is crucial. In the nEXO neutrinoless-double-β-decay experiment, the identification, or ‘tagging’, of the 136 Ba daughter atom resulting from the double-β decay of 136 Xe provides a technique for discriminating background. The tagging scheme studied here uses a cryogenic probe to trap the barium atom in a solid xenon matrix, where the barium atom is tagged through fluorescence imaging. Here we demonstrate the imaging and counting of individual barium atoms in solid xenon by scanning a focused laser across a solid xenon matrix deposited on a sapphire window. When the laser irradiates an individual atom, the fluorescence persists for about 30 seconds before dropping abruptly to the background level—a clear confirmation of one-atom imaging. Following evaporation of a barium deposit, the residual barium fluorescence is 0.16 per cent or less. Our technique achieves the imaging of single atoms in a solid noble element, establishing the basic principle of barium tagging for nEXO.
CRIS-Team Scopus Importer:2019-05-17

Imaging Quality Improvement by a Diffusively Scattering Screen - Leuchs, Gerd (Optik, 1996)
The quality of an image can be enhanced by using a stationary diffusively scattering screen placed in an intermediate image plane. Image impairment caused by small optical materials defects or dust particles is reduced. The effect is demonstrated using a microfilm reader.
UnivIS-Import:2015-03-05:Pub.1996.nat.dphy.optik.1optik.imagin

Imaging: Speckle and Coherence - Häusler, Gerd (Encyclopedia of Modern Optics, 2004)
UnivIS-Import:2015-04-20:Pub.2004.nat.dphy.optik.1optik.imagin

Impact of heating on passive and active biomechanics of suspended cells - Chan, C. J.; Whyte, Graeme; Boyde, L.; Salbreux, Guillaume; Guck, Jochen (Interface Focus, 2014)
A cell is a complex material whose mechanical properties are essential for its normal functions. Heating can have a dramatic effect on these mechanical properties, similar to its impact on the dynamics of artificial polymer networks. We investigated such mechanical changes by the use of a microfluidic optical stretcher, which allowed us to probe cell mechanics when the cells were subjected to different heating conditions at different time scales. We find that HL60/S4 myeloid precursor cells become mechanically more compliant and fluid-likewhen subjected to either a sudden laser-induced temperature increase or prolonged exposure to higher ambient temperature. Above a critical temperature of 52±1°C, we observed active cell contraction, which was strongly correlatedwith calciuminflux through temperature-sensitive transient receptor potential vanilloid 2 (TRPV2) ion channels, followed by a subsequent expansion in cell volume. The change from passive to active cellular response can be effectively described by a mechanical model incorporating both active stress and viscoelastic components. Our work highlights the role of TRPV2 in regulating the thermomechanical response of cells. It also offers insights into how cortical tension and osmotic pressure govern cell mechanics and regulate cell-shape changes in response to heat and mechanical stress. © 2014 The Author(s).
CRIS-Team Scopus Importer:2022-08-05
Keywords: Calcium; Cell contraction; Cell rheology; Cortical tension; Myeloid precursor cell; Optical stretcher

Implementation of a Scattering Method for Rough Surfaces in a Raytracing Software linked with a CAD (Computer-Aided Design) Toolbox - Loosen, Florian; Backhaus, Carsten; Lindlein, Norbert; Zeitler, Jochen Tobias; Franke, Jörg (Frontiers in Optics 2016, OSA Technical Digest (online) (Optical Society of America, 2016), paper FW3H.2, 2016)
The design and simulation of printed polymer optical waveguides is a new approach in the field of raytracing techniques, to link the CAD routines with the simulation process of the waveguides via raytracing methods.
Keywords: Polymer waveguides (130.5460); Propagating methods (220.2560); Scattering; rough surfaces (290.5880)

Important Parameters of Printed Polymer Optical Waveguides (POWs) in Simulation and Fabrication - Reitberger, Thomas; Franke, Jörg; Loosen, Florian; Lindlein, Norbert (Proc. SPIE 10098, Physics and Simulation of Optoelectronic Devices XXV, 100981B (February 22, 2017), 2017)
In this paper, polymer optical waveguides (POWs), fabricated by using flexographic printing for printing conditioning lines onto polymethylmethacrylate (PMMA) foil substrate material and Aerosol Jet Printing for producing the core and cladding of the waveguide, are characterized by using Monte Carlo raytracing for the scattering process. This method offers the opportunity to simulate the propagation of light, which are traced through the produced POWs. In the first step, the surface roughness of all optical materials, which are involved in the fabrication process of the POWs, are measured. The roughness measurement of substrate, core and cladding material is necessary to interlink the surface roughness (Monte Carlo scattering model) with a non-sequential raytracing method. Not only the surface of each material is investigated, but also the roughness measurement of the interlayer between the printed core and cladding material is examined. To build up the complete manufacturing technology virtually, also the process parameters of the printing need to be investigated. The results of the tracing must be a value of the attenuation of a simulated printed POW to give the designer a feedback about the optical quality of the waveguide before the printing process. This project is part of the DFG (the German Research Foundation) founded research group OPTAVER where the goal is to build up the whole manufacturing process, from the CAD, over the simulation, to the fabrication process and coupling of such printed POWs. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Keywords: Fabrication; Polymers; Simulations; Waveguides; Printing; Cladding; Scattering; Surface roughness; Manufacturing; Optical materials

Improved white-light interferometry on rough surfaces by statistically independent speckle patterns - Häusler, Gerd; Hybl, Ondrej; Wiesner, Bernhard (Applied Optics, 2012)
White-light interferometry (WLI) on rough surfaces is based on interference from individual speckles. The measurement uncertainty of WLI is limited by a random shift of these individual interference patterns. The statistical error in each measurement point depends on the brightness of the corresponding speckle: a dark speckle yields a larger error than a bright speckle. In this paper, a novel method is presented to reduce the measurement uncertainty significantly: by sequentially switching the direction of the illumination, the camera sees several independent speckle patterns in sequence. From each pattern, the brightest speckles are selected to eventually calculate an accurate height map. This height map displays no outliers, and the measured surface roughness is close to the stylus measurements.

Improvement of NOLM-based phase-preserving amplitude limiters by fiber optimizations - Stephan, C.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (Lasers and Electro-Optics (CLEO) and Quantum Electronics and Laser Science Conference (Qels), May, 2010)
lhft_intern.bib::Stephan10a

Improving the Optical Properties of Self-Catalyzed GaN Microrods toward Whispering Gallery Mode Lasing - Tessarek, Christian; Roeder, Robert; Michalsky, Tom; Geburt, Sebastian; Franke, Helena; Schmidt-Grund, Ruediger; Heilmann, Martin; Hoffmann, Bjoern; Ronning, Carsten; Grundmann, Marius; Christiansen, Silke (ACS Photonics, 2014)
GaN microrods were grown self-catalyzed by a fast and simple metal–organic vapor phase epitaxy method without any processing before or after deposition. The prismatic microrods with a regular hexagonal cross-section, sharp edges, straight, and smooth sidewall facets act as a microresonator, as seen by the appearance of whispering gallery modes in the yellow defect band range. To improve their optical properties, a reduced Ga precursor flow is required during growth. However, their hexagonal microrod morphology is not maintained under these growth conditions. The approach to start growth with a high Ga precursor flow and applying a ramp to a reduced precursor flow yield in significant enhancement of the near band edge emission in the upper part of the microrods. Whispering gallery modes in superposition with the near band edge emission can now be detected by cathodoluminescence measurements. These improvements lead to stimulated emission of a single whispering gallery mode up to ∼2 MW/cm2 and multimode lasing with a threshold of 2.86 MW/cm2 from an as-grown microrod under optical excitation at room temperature.
Keywords: GaN; growth; lasing; microrods; MOVPE; whispering gallery modes

Incoherent averaging of phase singularities in speckle-shearing interferometry - Mantel, Klaus Peter; Nercissian, Vanusch; Lindlein, Norbert (Optics Letters, 2014)

Indefinite-Mean Pareto Photon Distribution from Amplified Quantum Noise - Manceau, Mathieu; Spasibko, Kirill Yu; Leuchs, Gerd; Filip, Radim; Chekhova, Maria (Physical Review Letters, 2019)
Extreme events appear in many physics phenomena, whenever the probability distribution has a "heavy tail" differing very much from the equilibrium one. Most unusual are the cases of power-law (Pareto) probability distributions. Among their many manifestations in physics, from "rogue waves" in the ocean to Lévy flights in random walks, Pareto dependences can follow very different power laws. For some outstanding cases, the power exponents are less than 2, leading to indefinite values not only for higher moments but also for the mean. Here we present the first evidence of indefinite-mean Pareto distribution of photon numbers at the output of nonlinear effects pumped by parametrically amplified vacuum noise, known as bright squeezed vacuum (BSV). We observe a Pareto distribution with power exponent 1.31 when BSV is used as a pump for supercontinuum generation, and other heavy-tailed distributions (however, with definite moments) when it pumps optical harmonics generation. Unlike in other fields, we can flexibly control the Pareto exponent by changing the experimental parameters. This extremely fluctuating light is interesting for ghost imaging and for quantum thermodynamics as a resource to produce more efficiently nonequilibrium states by single-photon subtraction, the latter of which we demonstrate experimentally.
CRIS-Team Scopus Importer:2019-10-08

Inducing a detector efficiency mismatch to hack a commercial quantum key distribution system - Jain, N.; Lydersen, L.; Wittmann, C.; Wiechers, C.; Elser, D.; Marquardt, Christoph; Makarov, V.; Leuchs, Gerd (2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011, 2011)
Quantum key distribution (QKD) is poised to be the first widespread implementation of quantum communication. In principle, it offers unconditional security: an eavesdropper introduces errors and thus cannot remain concealed from the legitimate parties. However, in practical implementations the actual security depends on a host of technological and protocol-operational components. Eve could exploit imperfections in Alice's or Bob's equipment (such as source or detectors) remotely, or vulnerabilities in the actual implementation of the abstract QKD protocol. Several such attacks have been proposed [1,2], and various proof-of-principle demonstrations on commercial QKD devices have been performed in recent years [3-5]. © 2011 IEEE.
CRIS-Team Scopus Importer:2022-06-05

Influence of different gases on ionisation-induced refractive index changes in gas-filled hollow-core PCF - Koehler, Johannes R.; Köttig, Felix; Tani, Francesco; Russell, Philip St. John (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Recombination in gas ionised by femtosecond laser pulses generates heating and sound waves. The resulting transient refractive index changes can, at high enough laser repetition rates, affect propagation of successive pulses. In gas-filled hollow-core photonic crystal fibre (HC-PCF), where pulses with μ energies are sufficiently intense to ionise the gas, pulse-compression and UV-generation experiments revealed a clear dependence of the nonlinear dynamics on repetition rate [1]. In a recent study a probe laser was transmitted through a single-ring HC-PCF from the side to detect the single-shot temporal refractive index evolution [2]. The results suggest using atomically lighter gases to reduce detrimental ionisation effects, however capillary vibrations driven by plasma-induced sound waves caused additional probe-phase modulation which complicated a clear experimental proof.
CRIS-Team Scopus Importer:2019-11-15

Influence of group-velocity dispersion on multilevel phase-preserving amplitude regeneration in a nonlinear amplifying loop mirror - Röthlingshöfer, Tobias; Toth, Daniel; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Transparent Optical Networks (ICTON), 2012)
Numerical simulations have shown a significant influence of group-velocity dispersion (GVD) of the highly nonlinear fiber on the transfer characteristics of a nonlinear amplifying loop mirror (NALM). The effect is especially strong for the anomalous dispersion regime where an interaction of GVD and self-phase modulation (SPM) leads to formation of high-order solitons. The irregularities of the resulting NALM transfer functions can be used for phase-preserving amplitude regeneration of several, irregular-spaced amplitude states for multi-level modulation formats. The regeneration performance was estimated for a 16QAM signal with three amplitude states where a reduction of amplitude noise without significant signal phase distortions has been observe
lhft_intern.bib::Roethlingshoefer2012ca

Influence of Group Velocity Dispersion on phase-preserving Amplitude Regeneration by a Nonlinear Amplifying Loop Mirror - Sponsel, Klaus; Cvecek, Kristian; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Lasers and Electro-Optics, 2008 and Conference on Quantum Electronics and Laser Science, pages 1-2, 4 - 8 May, 2008)
The influence of dispersion of the highly nonlinear fiber in the loop of a nonlinear amplifying loop mirror on its performance as a 2R regenerator for phase-encoded optical signals has been studied. © 2008 Optical Society of Americ
UnivIS-Import:2017-12-18:Pub.2008.tech.IE.LEH.influe

Influence of Initial Surface Roughness on LIPSS Formation and Its Consecutive Impact on Cell/Bacteria Attachment for TiAl6V4 Surfaces - Sotelo, Lamborghini; Fontanot, Tommaso; Vig, Sanjana; Herre, Patrick; Yousefi, Peyman; Fernandes, Maria Helena; Sarau, George; Leuchs, Gerd; Christiansen, Silke (Advanced Materials Technologies, 2023)
The influence of the initial surface roughness of TiAl6V4 samples on the orientation and periodicity of the resulting laser-induced periodic surface structures (LIPSS), as well as the surface wettability and chemistry is reported here. Before LIPSS fabrication, initial sample surface roughness is adjusted by variations of finial polishing steps with polishing grain sizes of 18.3, 8.4, 5, and 0.5 µm. A 3 × 3 irradiation matrix was defined and lasered on all samples by changing the laser power and distance between consecutive laser scans. The resulting structures were characterized by scanning electron microscopy (SEM), atomic force microscopy, Raman spectroscopy, and contact angle measurements. As a further step, three representative generated structures were chosen to explore their bone implant viability by resazurin assays, alkaline phosphatase activity, and direct SEM imaging of the induced cells (MG63) and bacteria (Escherichia coli and Staphylococcus aureus). Results show that initial surface roughness has big influence on the wettability of the resulting surface, as well as inducing small variations on the orientation of the generated LIPSS. Structures generated with a higher integrated fluence have also shown to enhance cell differentiation while reducing bacterial activity, making them a great candidate for improved bone implant compatibility and durability.
CRIS-Team Scopus Importer:2023-04-20
Keywords: biocompatibility; laser functionalization; laser-induced periodic surface structures; TiAl6V4

Influence of Rayleigh Backscattering on the Performance of NOLM-Based Phase-Preserving Amplitude Limiters - Stephan, C.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (Conference on OFC / NFOEC, March, San Diego, 2010)
lhft_intern.bib::Stephan10b

Influence of Rayleigh Backscattering on the Performance of NOLM-Based Phase-Preserving Amplitude Limiters - Stephan, C.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (OSA Optics and Photonics Congress, Advanced Photonics, BGPP Topical Meeting, Karlsruhe, 21.-24. Juni, 2010)
lhft_intern.bib::Stephan10

Influence of surface tension and inner pressure on the process of fibre drawing - Luzi, Giovanni; Epple, Philipp; Scharrer, Michael; Fujimoto Meinecke, Ken; Rauh, Cornelia; Delgado, Antonio (Journal of Lightwave Technology, 2010)
The present contribution deals with thermofluidynamical features occurring during the drawing of capillaries for microstructured optical fibres. Here, the process stability depends strongly on flow and thermal processes taking place as a preform is heated and drawn in the furnace. This is the case particularly for hollow fibres for which the existence of the inner hole directly depends on material parameters such as the surface tension and the rheological properties and on process parameter such as hole internal pressure and the process temperature. A fluid-mechanics model suggested in the literature that makes use of asymptotic analysis based on small aspect ratio of the micro capillaries, has been revisited and improved recently and the leading-order equations have been then examined in some asymptotic limits by Luzi et al.. Starting from the novel class of solutions of the simplified equations of motion the present paper focuses on the effect of both surface tension and internal hole pressure since those are of essential importance during drawing. Thus, comparisons with experimental data are performed, in order to validate the analytical model developed in , which will be briefly presented here. The theoretical model gives very accurate predictions both when the internal hole is pressurized or when no pressure is applied, as long as the temperature does not reach too high values. © 2006 IEEE.
UnivIS-Import:2015-03-09:Pub.2010.tech.ITC.stmmec.influe
Keywords: Asymptotic analysis; Holey fibres; Micro structured optical fibres (MOFs); Numerical methods; Photonic crystal fibres

Influence on the optical performance of droplets and enclosures in printed polymer optical waveguides - Backhaus, Carsten; Förner, Johannes; Wienke, Alexander; Hoffmann, Gerd-Albert; Eiche, Yannic; Lorenz, Lukas; Kaierle, Stefan; Overmeyer, Ludger; Franke, Jörg; Bock, Karlheinz; Lindlein, Norbert (Physics and Simulation of Optoelectronic Devices XXIX, 2021)
Printing polymer optical waveguides by means of combined printing processes has proven to be a challenging but effective way of producing waveguides with a loss less than 0.3dB/cm. In order to evaluate the optical performance of the produced waveguides, optical simulations have been carried out. In this work we show the influence on the optical performance by simulating droplets and enclosures in multimode waveguides with a proprietary raytracing algorithm. Critical waveguide parameters such as width and height variation will be evaluated. Finally, experimentally achieved optical performance is presented and compared with the simulation resul
Keywords: Raytracing; Polymer Optical Waveguides; Aerosol Jet Printing; Optical Simulation; Waveguide Quality Analysis; Signal Attenuation; Waveguides; 3D Printing

Information theoretical optimization for optical range sensors, - Häusler, Gerd; et al. (Applied Optics, 2003)
Most of the known optical range sensors require a large amount of two-dimensional raw data from which the three-dimensional (3D) data are decoded and so are associated with considerable cost. The cost arises from expensive hardware as well as from the time necessary to acquire the images. We will address the question of how one can acquire maximum shape information with a minimum amount of image raw data, in terms of information theory. It is shown that one can greatly reduce the amount of raw data needed by proper optical redundancy reduction. Through these considerations, a 3D sensor is introduced, which needs only a single color (red-green-blue) raw image and still delivers data with only approximately 2-μm longitudinal measurement uncertainty. © 003 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2003.nat.dphy.optik.1optik.inform

Innovative optical components and their impact on future transmission systems - Schmauß, Bernhard; Striegler, Arne; Meißner, Markus (Invited talk, APOC, Wuhan, China, November, 2003)
Optical transmission systems made impressive progress in the field of system capacity, reach and flexibility. Beside all improvements achieved so far, signal distortion on the one hand side and noise accumulation on the other hand side are the limitations of optical transmission system performance. In terms of signal distortion besides advanced link design strategies optical regenerators are of high interest for signal conditioning along a fiber link. Our paper reviews signal regeneration techniques focusing on fiber nonlinearity based setups both in interferometric and non interferometric architecture. We analyze the impact of regenerator design parameters as fiber nonlinear parameters, regenerator input power and characteristics of filters on signal improvement and demonstrate e.g. the increase of system reach. In order to address the upcoming techniques of advanced modulation formats we introduce a fiber based regenerator scheme that shows attractive potential especially for phase modulated signals. Combining these new optical formats with regenerative methods is attractive for high performance systems. For the differential phase shift keying (DPSK) modulation format we investigate the potential of a cross phase modulation based type of regenerator in more detail. The availability of suitable regenerator components, especially highly nonlinear fibers is one of the challenges. Especially the new fiber types known as photonic crystal fibers can act as bases for new structures and thus will open the door for ultra high performance optical transmission systems.
UnivIS-Import:2015-04-16:Pub.2003.tech.IE.LEH.innova
Keywords: Modulation Format; Optical Transmission; Regeneration

Inorganic photovoltaics - Planar and nanostructured devices - Ramanujam, Jeyakumar; Verma, Amit; Gonzalez-Diaz, B.; Guerrero-Lemus, Ricardo; Del Canizo, Carlos; Garcia-Tabares, Elisa; Rey-Stolle, Ignacio; Granek, Filip; Korte, Lars; Tucci, Mario; Rath, Jatin; Singh, Udai P.; et al. (Progress in Materials Science, 2016)
Since its invention in the 1950s, semiconductor solar cell technology has evolved in great leaps and bounds. Solar power is now being considered as a serious leading contender for replacing fossil fuel based power generation. This article reviews the evolution and current state, and potential areas of near future research focus, of leading inorganic materials based solar cells, including bulk crystalline, amorphous thin-films, and nanomaterials based solar cells. Bulk crystalline silicon solar cells continue to dominate the solar power market, and continued efforts at device fabrication improvements, and device topology advancements are discussed. III-V compound semiconductor materials on c-Si for solar power generation are also reviewed. Developments in thin-film based solar cells are reviewed, with a focus on amorphous silicon, copper zinc tin sulfide, cadmium telluride, as well as nanostructured cadmium telluride. Recent developments in the use of nano-materials for solar power generation, including silicon and gallium arsenide nanowires, are also reviewed.

Inorganic photovoltaics – Planar and nanostructured devices - Ramanujam, Jeyakumar; Verma, Amit; Gonzalez-Diaz, B.; Guerrero-Lemus, Ricardo; Del Canizo, Carlos; Garcia-Tabares, Elisa; Rey-Stolle, Ignacio; Granek, Filip; Korte, Lars; Tucci, Mario; Rath, Jatin; Singh, Udai P.; et al. (Progress in Materials Science, 2016)
<ul class="issue-navigation" style="margin: 0px 0px 16px; padding-right: 0px; padding-left: 0px; box-sizing: border-box; list-style: none; background: rgb(245, 245, 245); overflow: hidden; color: rgb(80, 80, 80); font-family: Arial, Helvetica, "Lucida Sans Unicode", "Microsoft Sans Serif", "Segoe UI Symbol", STIXGeneral, "Cambria Math", "Arial Unicode MS", sans-serif; font-size: medium;"> <div class="Abstracts" style="margin: 0px; padding: 0px; box-sizing: border-box; line-height: 24px; color: rgb(80, 80, 80); font-family: Arial, Helvetica, "Lucida Sans Unicode", "Microsoft Sans Serif", "Segoe UI Symbol", STIXGeneral, "Cambria Math", "Arial Unicode MS", sans-serif; font-size: medium;"> Since its invention in the 1950s, semiconductor solar cell technology has evolved in great leaps and bounds. Solar power is now being considered as a serious leading contender for replacing fossil fuel based power generation. This article reviews the evolution and current state, and potential areas of near future research focus, of leading inorganic materials based solar cells, including bulk crystalline, amorphous thin-films, and nanomaterials based solar cells. Bulk crystalline silicon solar cells continue to dominate the solar power market, and continued efforts at device fabrication improvements, and device topology advancements are discussed. III–V compound semiconductor materials on c-Si for solar power generation are also reviewed. Developments in thin-film based solar cells are reviewed, with a focus on amorphous silicon, copper zinc tin sulfide, cadmium telluride, as well as nanostructured cadmium telluride. Recent developments in the use of nano-materials for solar power generation, including silicon and gallium arsenide nanowires, are also reviewed.

In Process 3D-Sensing for Laser Material Processing - Häusler, Gerd; et al. (Proc. of Third International Conference on 3D Digital Imaging and Modeling, 2001)
UnivIS-Import:2015-04-16:Pub.2001.forsch.gradui.gradui_6.inproc

In Situ Heterogeneous Catalysis Monitoring in a Hollow-Core Photonic Crystal Fiber Microflow Reactor - Cubillas, Ana Maria; Schmidt, Matthias; Euser, Tijmen G.; Taccardi, Nicola; Unterkofler, Sarah; Russell, Philip St. John; Wasserscheid, Peter; Etzold, Bastian (Advanced Materials Interfaces, 2014)
A novel process for uniform deposition of noble-metal catalyst nanoparticles on the inner core wall of a hollow-core photonic crystal fiber is presented. The resulting continuous flow microreactor enables heterogeneous catalysis reactions on extremely low (sub- extgreekmL) sample volumes. Strikingly, the excellent single mode transmission properties of the HC-PCF are preserved after the deposition process, allowing sensitive in situ spectroscopy measurements over unprecedented length scales of up to 50 cm.

In-situ monitoring of homogeneously catalysed reactions using raman spectroscopy inside hollow-core photonic crystal fibres - Schorn, Florian; Aubermann, Manfred; Zeltner, Richard; Wasserscheid, Peter; Haumann, Marco; Joly, Nicolas (Optics InfoBase Conference Papers, 2020)
We monitor the reaction of an acid with an alcohol inside a hollow-core photonic crystal fibre using Raman spectroscopy. The method uses tiny amount of chemicals and allows precise measurement of the activation energy.
CRIS-Team Scopus Importer:2020-11-13

In-Situ surface characterization of nano- and microparticles by optical Second Harmonic Generation - Schürer, Benedikt; Wunderlich, Sarina; Peschel, Ulf; Peukert, Wolfgang (Nanotechnology 2010: Advanced Materials, CNTs, Particles, Films and Composites, 2010)
Nonlinear optical spectroscopic techniques, namely Second Harmonic Generation (SHG) spectroscopy and Sum Frequency Generation (SFG), are highly interface sensitive and can be used to obtain information exclusively from the surface of particles. Second Harmonic Generation (SHG) has proven to be a versatile technique that can be used to probe different kinds of surface properties of dispersed particle systems in in-situ. Prominent examples are the direct study of molecular adsorption at the surface of particles and the determination of surface potentials of nano- and microparticles. However, in most of these studies well-defined spherical and monodisperse particles with low number densities were used. Here we demonstrate the application of the SHG technique for the study of more complex and technically relevant particle systems. We discuss the influence of particle concentration and particle size distribution. Moreover, we apply a novel nonlinear Mie Model that is capable to simulate the SH scattering from the surface of spherical particles and we show that the model can be used to extract information about molecules at the particle liquid interfac
Keywords: Nonlinear Mie model; Nanoparticles; Second Harmonic Generation; Optics; Surface characterization

Instantaneous speckle reduction? Yes, but there is no free lunch! - Häusler, Gerd; Dötzer, Florian; Mantel, Klaus (Proceedings of SPIE - The International Society for Optical Engineering, 2018)
We are motivated by the question if scanning laser projection with low speckle noise is possible. Scanning laser projection requires "instantaneous" speckle reduction, within a few nanoseconds-meaning that no moving diffusors can be used. We will argue that instantaneous speckle reduction is possible by conversion of spatial coherence to spatial incoherence-but nature demands for a compensation. The cost can be estimated via the information theoretical concept "channel capacity", which incorporates the etendue as well as the signal-to-noise ratio. We will show that an optical system with low spatial coherence (=low speckle noise) must provide significantly more degrees of freedom than a coherent imaging system. The consequence for the technical optical system is serious: Significant speckle reduction can only be achieved by an excessively large projection aperture. This is not just a sophistic consideration, it seriously restricts the design of scanning laser projectors.
Created from Fastlane, Scopus look-up
Keywords: Channel capacity; Etendue; Laser projection; Speckle noise; Speckle noise reduction

Integrated Photonics for Quantum Communication on a Cubesat - Pudelko, Jonas; Bayraktar, Ömer; Khan, Imran; Boxleitner, Winfried; Petscharnig, Stefan; Pacher, Christoph; Leuchs, Gerd; Marquardt, Christoph (2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2023)
The limited range of quantum key distribution (QKD) in fiber based systems led to several projects aiming for the development of a satellite based QKD infrastructure, like the conduction of quantum limited measurements from a geostationary satellite [1] or the MICIUS mission, which impressively demonstrated QKD on a global scale [2]. However, due to the high costs of satellite launches the profitability of commercial systems would benefit dramatically from further reduction in size, weight and power. Photonic integration [3] addresses these points by allowing the integration of all optical components of a QKD system on a photonic integrated circuit (PIC). In this work, we are going to demonstrate building blocks for quantum communication from space based on photonic integration technology by building a payload for the CubeSat mission QUBE [4] consisting of an integrated sender for weak coherent states as well as an integrated Quantum Random Number Generator (QRNG).<br

Interacting waves on chains of split-ring resonators in the presence of retardation - Lomanets, Vadym; Zhuromskyy, Oleksandr; Onishchukov, Georgy; Sydoruk, Oleksiy; Tatartschuk, Eugen; Shamonina, E.; Leuchs, Gerd; Peschel, Ulf (Applied Physics Letters, 2010)
Wave propagation is studied experimentally in a one-dimensional periodic chain of magnetically coupled split-ring resonators with a spacing of about one tenth of the resonant wavelength. Retardation leads to a strong interaction between magnetoinductive and free-space waves. Two kinds of guided modes are observed: a slow backward wave which propagates far outside the light cone, and a fast forward wave close to the light cone. The two merge in a region of zero group velocity. The results are relevant for all one- and two-dimensional periodic systems interacting with waves of the surrounding space.
EAM Import::2019-03-13

Interaction of highly focused vector beams with a metal knife-edge - Marchenko, P.; Orlov, S.; Huber, C.; Banzer, Peter; Quabis, Susanne; Peschel, Ulf; Leuchs, Gerd (Optics Express, 2011)
We investigate the interaction of highly focused linearly polarized optical beams with a metal knife-edge both theoretically and experimentally. A high numerical aperture objective focusses beams of various wavelengths onto samples of different sub-wavelength thicknesses made of several opaque and pure materials. The standard evaluation of the experimental data shows material and sample dependent spatial shifts of the reconstructed intensity distribution, where the orientation of the electric field with respect to the edge plays an important role. A deeper understanding of the interaction between the knife-edge and the incoming highly focused beam is gained in our theoretical model by considering eigenmodes of the metal-insulator-metal structure. We achieve good qualitative agreement of our numerical simulations with the experimental findings.
EAM Import::2019-03-13

Interaction of light carrying orbital angular momentum with a chiral dipolar scatterer - Wozniak, Pawel; De Leon, Israel; Hoeflich, Katja; Leuchs, Gerd; Banzer, Peter (Optica, 2019)
The capability to distinguish the handedness of circularly polarized light is a well-known intrinsic property of a chiral nanostructure. It is a long-standing controversial debate, however, whether a chiral object can also sense the vorticity, or the orbital angular momentum (OAM), of a light field. Since OAM is a spatial property, it seems rather counter-intuitive that a point-like chiral object could be able to distinguish the sense of the wave-front of light carrying OAM. Here, we show that a dipolar chiral nanostructure is indeed capable of distinguishing the sign of the phase vortex of the incoming light beam. To this end, we take advantage of the conversion of the sign of OAM, carried by a linearly polarized Laguerre-Gaussian beam, into the sign of optical chirality upon tight focusing. Our study provides for a deeper insight into the discussion of chiral light-matter interactions and the respective role of OAM. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
CRIS-Team WoS Importer:2019-09-13

Interaction of light with hematite hierarchical structures: Experiments and simulations - Distaso, Monica; Zhuromskyy, Oleksandr; Seemann, Benjamin; Pflug, Lukas; Mackovic, Mirza; Encina, Ezequiel Roberto; Klupp Taylor, Robin; Müller, Rolf; Leugering, Günter; Spiecker, Erdmann; Peschel, Ulf; Peukert, Wolfgang (Journal of Quantitative Spectroscopy & Radiative Transfer, 2017)
Mesocrystalline particles have been recognized as a class of multifunctional materials with potential applications in different fields. However, the internal organization of nanocomposite mesocrystals and its influence on the final properties have not yet been investigated. In this paper, a novel strategy based on electrodynamic simulations is developed to shed light on how the internal structure of mesocrystals influences their optical properties. In a first instance, a unified design protocol is reported for the fabrication of hematite/PVP particles with different morphologies such as pseudo-cubes, rods-like and apple-like structures and controlled particle size distributions. The optical properties of hematite/PVP mesocrystals are effectively simulated by taking their aggregate and nanocomposite structure into consideration. The superposition T-Matrix approach accounts for the aggregate nature of mesocrystalline particles and validate the effective medium approximation used in the framework of the Mie theory and electromagnetic simulation such as Finite Element Method. The approach described in our paper provides the framework to understand and predict the optical properties of mesocrystals and more general, of hierarchical nanostructured particles.
Keywords: Effective medium approximation; FEM; Maxwell-Garnett theory; Mesocrystals; Scattering; T-Matrix

Interactive screen experiments with single photons - Bronner, Patrick; Strunz, Andreas; Silberhorn, Christine; Meyn, Jan-Peter (European Journal of Physics, 2009)
Single photons are used for fundamental quantum physics experiments as well as for applications. Originally being a topic of advance courses, such experiments are increasingly a subject of undergraduate courses. We provide interactive screen experiments (ISE) for supporting the work in a real laboratory, and for students who do not have access to a quantum optics laboratory. The main focus of the ISE is on undergraduate education, but some of the experiments are suitable for other levels of higher education as well. © 2009 IOP Publishing Lt
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.PI.PDP.intera

Interfacing transitions of different alkali atoms and telecom bands using one narrowband photon pair source - Schunk, Gerhard; Vogl, Ulrich; Strekalov, Dmitry V.; Förtsch, Michael; Sedlmeir, Florian; Schwefel, Harald; Göbelt, Manuela; Christiansen, Silke; Leuchs, Gerd; Marquardt, Christoph (Optica, 2015)
Quantum information technology strongly relies on the coupling of optical photons with narrowband quantum systems, such as quantum dots, color centers, and atomic systems. This coupling requires matching the optical wavelength and bandwidth to the desired system, which presents a considerable problem for most available sources of quantum light. Here we demonstrate the coupling of alkali dipole transitions with a tunable source of photon pairs. Our source is based on spontaneous parametric downconversion in a triply resonant whispering gallery mode resonator. For this, we have developed novel wavelength-tuning mechanisms that allow a coarse tuning to either the cesium or rubidium wavelength, with subsequent continuous fine-tuning to the desired transition. As a demonstration of the functionality of the source, we performed a heralded single-photon measurement of the atomic decay. We present a major advance in controlling the spontaneous downconversion process, which makes our bright source of heralded single photons now compatible with a plethora of narrowband resonant system
Keywords: Atomic; Quantum communications; Quantum optics; Spectroscopy

Interference between two coherently driven monochromatic terahertz sources - Preu, Sascha; Malzer, Stefan; Döhler, Gottfried; Zhao, Quanzhong; Hanson, Micah; Zimmerman, Jeremy; Gossard, Art; Wang, Lijun (Applied Physics Letters, 2008)
We report the interference between two phase-locked, continuous-wave, and coherent terahertz (Thz) photomixers. Both spatial and temporal coherence are observed with a narrow linewidth of less than 10 MHz. Phase locking is achieved by using one pair of lasers for both sources. The concept of optical narrow linewidth (fiber) distribution of the mixing signal opens various applications. We outline the necessary steps to extend this scheme for very long base line interferometric THz detection in the tens of kilometer range and for the improvement of spatial resolution for active stand-off THz imaging. © 2008 American Institute of Physics.

Interference of two intense entanglement sources: entanglement swapping and multi-partite entanglement - Glöckl, Oliver; Lorenz, Stefan; Marquardt, Christoph; Heersink, Joel; Pan, Quing; van Loock, Peter; Korolkova, Natalia; Leuchs, Gerd (2003 European Quantum Electronics Conference. EQEC 2003, 2003)
Progress of entanglement swapping experiment is reported. Four highly correlated modes are created by the interference of two entangled systems. As calculations show, there are strong hints that the state is indeed multi-partite entangled.<br
Keywords: Quantum entanglement; Physics; Hilbert space; Telecommunication standards; Cryptography; Teleportation

Interferenz von Licht macht einzelne unmarkierte Proteine sichtbar - König, Katharina; Gemeinhardt, André; Sandoghdar, Vahid (BioSpektrum, 2019)
iSCAT microscopy is a powerful tool for the optical detection and visualization of small nanoparticles, down to single unlabeled proteins. In this overview, we give an introduction to the method’s principles and benefits and show how it can be applied to monitor protein secretion of single living cells with single-protein sensitivity at millisecond temporal resolution.
CRIS-Team Scopus Importer:2019-12-13

Interferometrical measurement of cylindrical lenses with the help of computer generated holograms - Lindlein, Norbert; et al. (Proceedings of SPIE, 2001)
Two different methods for the measurement of cylindrical lenses will be presented in this paper. The first method uses the principle of grazing incidence interferometry. A computer generated diffractive optical element (DOE) generates the wave fronts which impinge under grazing incidence onto the surfaces to be tested. The light is reflected at the surfaces and diffracted at a second DOE identical to the first one. The 0-th diffraction order of both DOEs is used as reference wave. The deviations of up to three surfaces (front-side, backside and one of the border sides) of a cylindrical lens from their ideal shape can be measured simultaneously. Additionally, the orientation of these three surfaces with respect to each other are determined. The second method measures the aberrations of a cylindrical lens in transmitted light by using an interferometer of the Mach-Zehnder type. The cylindrical wave of the lens under test is compensated by a DOE which generates a plane wave if the incident wave is an ideal cylindrical wave. So, the wave aberrations of the cylindrical lens can be measured. The set-up is designed for cylindrical lenses with a high numerical aperture of up to 0.8. The principles of both methods and first experimental results will be presented.
UnivIS-Import:2015-04-14:Pub.2001.nat.dphy.optik.1optik.interf
Keywords: Computer generated holograms; Grazing incidence interferometry; Interferometry; Mach-Zehnder interferometer; Testing of aspherics; Testing of cylindrical lenses

Interferometric grazing incidence test of rough steep convex aspherics: full 3D reconstruction of the object - Rothau, Sergey; Schamburek, Tobias; Mantel, K.; Lindlein, Norbert (Applied Optics, 2022)
A grazing incidence interferometric measurement procedure is applied to test rough convex steep rotationally symmetric aspherics. The measurement of rough surfaces is possible; i.e., without the need to polish the surfaces, due to the large effective wavelength (λeff = 10 µm) of the test. One measurement step using diffractive beam splitters and phase-shifting techniques delivers the surface information along one meridian. The full surface description can be stitched together from several phase results combined with appropriate object rotations. This publication includes, besides the short recapitulation of the measurement principle and experimental setup, a presentation of the simulated and measured data of an aspherical object under test. The data analysis of each meridian is focused on the elimination of the misalignment aberrations caused by specimen displacements. Finally, the stitching of multiple meridian regions to a 3D surface map of the specimen is shown.
CRIS-Team Scopus Importer:2022-06-03

Interferometric grazing incidence test of rough steep convex spherical and aspherical surfaces: First simulations and experimental proof of principle - Rothau, Sergey; Lindlein, Norbert; Schwider, Johannes (Applied Optics, 2019)
In the past, grazing incidence interferometry has been applied for rough plane, cylindrical, acylindrical, and general rod-like surfaces using diffractive beam splitters. Here, we demonstrate that also rough convex steep rotational symmetric spherical or aspherical surfaces can be measured along one meridian in a single step using diffractive beam splitters and phase-shifting techniques. The extension to the whole surface can be attained by successive meridional measurements of the surface under test by azimuthal adjustments. The principle of the method is given and for a spherical ball lens as an extremely curved surface simulated, and experimental data are presented. The features of the interferogram are discussed, and the experimental evaluation of a single meridian including the unwrapped phase data is shown.
CRIS-Team Scopus Importer:2019-11-29

Interferometric grazing incidence test of rough steep convex spherics: Experimental data analysis - Rothau, Sergey; Mantel, K.; Lindlein, Norbert (Applied Optics, 2021)
Grazing incidence interferometry has been applied to plane, cylindrical, acylindrical, and general rod-like surfaces using diffractive beam splitters. Here, in a first step towards measuring aspherics, we demonstrate that also rough convex steep rotationally symmetric spherics can be measured along one meridian in a single step using diffractive beam splitters and phase shifting techniques. The measurement of rough surfaces is possible, i.e., without the need to polish the surfaces, due to the large effective wavelength (λeff ≈ 10 µm) of the test. We include, besides the short recapitulation of the measurement principle and experimental setup, a presentation of the measured data of one small meridian region for the special case of spherical objects under test. The subsequent data analysis combined with suitable simulations focuses on elimination of the misalignment aberrations from the results caused by specimen displacements in the setup.
CRIS-Team Scopus Importer:2021-01-08

Interferometric homogeneity test using adaptive frequency comb illumination - Mantel, Klaus Peter; Schwider, Johannes (Applied Optics, 2013)

Interferometric Homogeneity Test Using Adaptive Frequency Comb Illumination - Mantel, Klaus Peter; Schwider, Johannes (Fringe 2013, 2013)

Interferometric measurement of holographic lenslets - Lindlein, Norbert; et al. (Journal of Modern Optics, 1993)
A holographic optical element can either be characterized by the wave aberrations or by the point spread function or alternatively by the modulation transfer function. Here we propose the measurement of the wave aberrations with the help of a Twyman-Green interferometer adapted to the requirements for testing holographic optical elements. The evaluation of the interferograms is done with the phase-shifting technique. The resulting wave aberrations are expressed by Zemike coefficients. In addition to this evaluation, the point spread function and the modulation transfer function are calculated from the wave aberrations. The set-up, the evaluation method and also exemplary results of a tested holographic optical element are presented. © 1993 Taylor & Francis Ltd.

Interferometric measurement of micro-lenses including cylindrical lenses - Lindlein, Norbert; Lamprecht, Jürgen; Schwider, Johannes (Microoptics, 2004)
UnivIS-Import:2015-04-20:Pub.2004.nat.dphy.optik.1optik.interf

Interferometric null test of a deep parabolic reflector generating a Hertzian dipole field - Leuchs, Gerd; Mantel, Klaus; Berger, Andreas; Konermann, Hildegard; Sondermann, Markus; Peschel, Ulf; Lindlein, Norbert; Schwider, Johannes (Applied Optics, 2008)
We report on interferometric characterization of a deep parabolic mirror with a depth of more than five times its focal length. The interferometer is of Fizeau type; its core consists of the mirror itself, a spherical null element, and a reference flat. Because of the extreme solid angle produced by the paraboloid, the alignment of the setup appears to be very critical and needs auxiliary systems for control. Aberrations caused by misalignments are removed via fitting of suitable functionals provided by means of ray tracing simulations. It turns out that the usual misalignment approximations fail under these extreme conditions.© 2008 Optical Society of America.
UnivIS-Import:2015-04-14:Pub.2008.nat.dphy.optik.1optik.interf

Interferometric null test of a parabolic reflector generating a Hertzian dipole field - Lindlein, Norbert; et al. (Interferometry XIV: Techniques and Analysis, 2008)
Interferometric surface tests of stigmatic aspherics can be carried out in a null test configuration. Null tests require reference null elements either plane or spherical surfaces or both. A parabolic reflector transforms a plane into a spherical wave which converges to the focus of the paraboloid. Therefore, a spherical ball lens or a steel ball can be placed into the focus enabling a double-pass geometry for the null test. Here a Fizeau interferometer geometry has been selected in order to guarantee invariance against polarization distortions under the assumption that radially polarized laser light is used for the interferometer. Radial polarized light is necessary to mimic a Hertzian dipole field. Due to the extreme solid angle produced by the paraboloid the alignment of the setup is very critical and needs auxiliary systems for the control. Aberrations caused by misalignments are removed via fitting of suitable functional provided through ray-trace simulations. It turned out that the usual vector approximations fail under these extreme circumstances. Test results are given for a paraboloid with 2mm focal length transforming a plane wave into a near dipole wave comprising a solid angle of about 3,4π.

Interferometric quasi-absolute tests for aspherics using a radial shear position - Mantel, Klaus Peter; Geist, Eduard; Harder, Irina; Lindlein, Norbert; Leuchs, Gerd (Optics Letters, 2009)
Increasing accuracy requirements in aspheric metrology make the development of absolute testing procedures for aspheric surfaces important. One strategy is transferring the standard practice three-position test for spheres to aspherics. The three-position test, however, involves a cat's eye position and therefore has certain drawbacks. We propose an absolute testing method for rotationally symmetric aspherics where the cat's eye position is replaced with a radially sheared position. Together with rotational movements of the specimen, the surface deviations can be obtained in an absolute manner. To demonstrate the validity of the procedure, we present a measurement result for a sphere and compare it with a result obtained by the standard three-position test. © 2009 Optical Society of America.
UnivIS-Import:2015-04-14:Pub.2009.nat.dphy.optik.1optik.interf

Interferometric scattering microscopy reveals microsecond nanoscopic protein motion on a live cell membrane - Taylor, Richard W.; Mahmoodabadi, Reza Gholami; Rauschenberger, Verena; Gießl, Andreas; Schambony, Alexandra; Sandoghdar, Vahid (Nature Photonics, 2019)
Many of the biological functions of a cell are dictated by the intricate motion of proteins within its membrane over a spatial range of nanometres to tens of micrometres and time intervals of microseconds to minutes. This rich parameter space is not accessible by fluorescence microscopy, but it is within reach of interferometric scattering (iSCAT) particle tracking. However, as iSCAT is sensitive even to single unlabelled proteins, it is often accompanied by a large speckle-like background, which poses a substantial challenge for its application to cellular imaging. Here, we employ a new image processing approach to overcome this difficulty and demonstrate tracking of transmembrane epidermal growth factor receptors with nanometre precision in all three dimensions at up to microsecond speeds and for durations of tens of minutes. We provide examples of nanoscale motion and confinement in ubiquitous processes such as diffusion in the plasma membrane, transport on filopodia and rotational motion during endocytosis.
CRIS-Team Scopus Importer:2019-05-02

Interferometric testsfor micro-optics - Lindlein, Norbert; Schwider, Johannes (1996)
UnivIS-Import:2015-03-05:Pub.1996.nat.dphy.optik.1optik.interf_5

Interferometrie in streifender Inzidenz an Asphären - Rothau, Sergej; Schamburek, Tobias; Lindlein, Norbert (122, 2021)

Interferometrie in streifender Inzidenz: Simulationen und Messergebnisse - Rothau, Sergej; Schwider, Johannes; Mantel, Klaus; Lindlein, Norbert (120. Annual Meeting of the DGaO, 2019)

Interferometrischer 3D-Sensor zur berührungslosen Vermessung technischer Oberflächen - Leuchs, Gerd; et al. (VDI-Berichte, 2000)
We demonstrate interferometric 3D-measurements of technical objects with rough surfaces. Objects with heights of a few millimetres up to several centimetres are measured from a distance of about one meter. With an integration time of 60ms a distance resolution of a few 10μm is achieved.
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.interf_89

Interferometry Simultaneous Measurement of the Surfaces of Cylindrical Lenses by Grazing Incidence Interferometry - Mantel, Klaus Peter; Lindlein, Norbert; Schwider, Johannes (VDI-Berichte, 2002)
Fabrication errors of cylindrical lenses may be divided into two categories: surface deviations and errors in the position and orientation of the surfaces relative to each other. A simultaneous measurement of both error sources is possible by means of grazing incidence interferometry. Thereby, the surface deviations and the misalignment errors of each surface relative to the diffractive null elements can be acquired for up to three surfaces at the same time. The misalignment errors provide information about the relative position of the surfaces and allow the detection of various error types like wedge errors and centering errors.
UnivIS-Import:2015-04-14:Pub.2002.nat.dphy.optik.1optik.interf_4

Inter-pulse dynamics at high repetition rates by femtosecond ionization in gas-filled fibres - Köttig, Felix; Koehler, Johannes R.; Tani, Francesco; Russell, Philip St. John (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Nonlinear propagation of intense ultrashort laser pulses in gases is mostly understood to be influenced only by the pulse itself, i.e., by single-shot dynamics, because relaxation processes are typically faster than the time between pulses. Using single-ring hollow-core photonic crystal fibre (PCF) [1], strong-field intensities can be reached by μ-level pulses, available from MHz-level repetition rate fibre lasers. At these high repetition rates it is not clear that pulse-to-pulse interactions can still be neglected. Indeed, experiments involving photoionization show a strong repetition rate-dependence, suggesting that the pulse dynamics are influenced by inter-pulse effects [1]. Recently it has been shown, using interferometric side-probing [2], that fs photoionization and subsequent recombination-induced heating leads to a drop in refractive index tens of μs long, caused by a gas density depression in the core after an acoustic shock wave has propagated away. Here we report that this modifies the characteristics of the fibre, influencing pulse propagation even at 100 kHz repetition rate.
CRIS-Team Scopus Importer:2019-11-15

Intracavity Squeezing Can Enhance Quantum-Limited Optomechanical Position Detection through Deamplification - Peano, Vittorio; Schwefel, Harald; Marquardt, Christoph; Marquardt, Florian (Physical Review Letters, 2015)
It has been predicted and experimentally demonstrated that by injecting squeezed light into an optomechanical device, it is possible to enhance the precision of a position measurement. Here, we present a fundamentally different approach where the squeezing is created directly inside the cavity by a nonlinear medium. Counterintuitively, the enhancement of the signal-to-noise ratio works by deamplifying precisely the quadrature that is sensitive to the mechanical motion without losing quantum information. This enhancement works for systems with a weak optomechanical coupling and/or strong mechanical damping. This can allow for larger mechanical bandwidth of quantum-limited detectors based on optomechanical devices. Our approach can be straightforwardly extended to quantum nondemolition qubit detection.
CRIS-Team Scopus Importer:2022-06-05

Investigating plasmonic gap modes coupled to nanoantennas - Wen, J.; Kriesch, Arian; Ploss, Daniel; Banzer, Peter; Schmauß, Bernhard; Peschel, Ulf (Lasers and Electro-Optics Europe (CLEO EUROPE/EQEC), 2011 Conference on and 12th European Quantum Electronics Conference, 2011)
lhft_intern.bib::Wen2011

Investigating the Optical Properties of a Laser Induced 3D Self-Assembled Carbon–Metal Hybrid Structure - Butt, Muhammad Abdullah; Lesina, Antonino Calà; Neugebauer, Martin; Bauer, Thomas; Ramunno, Lora; Vaccari, Alessandro; Berini, Pierre; Petrov, Yuriy; Danilov, Denis; Manshina, Alina; Banzer, Peter; Leuchs, Gerd (Small, 2019)
Carbon-based and carbon–metal hybrid materials hold great potential for applications in optics and electronics. Here, a novel material made of carbon and gold–silver nanoparticles is discussed, fabricated using a laser-induced self-assembly process. This self-assembled metamaterial manifests itself in the form of cuboids with lateral dimensions on the order of several micrometers and a height of tens to hundreds of nanometers. The carbon atoms are arranged following an orthorhombic unit cell, with alloy nanoparticles intercalated in the crystalline carbon matrix. The optical properties of this metamaterial are analyzed experimentally using a microscopic Müller matrix measurement approach and reveal a high linear birefringence across the visible spectral range. Theoretical modeling based on local-field theory applied to the carbon matrix links the birefringence to the orthorhombic unit cell, while finite-difference time-domain simulations of the metamaterial relates the observed optical response to the distribution of the alloy nanoparticles and the optical density of the carbon matrix.
CRIS-Team Scopus Importer:2019-05-02
Keywords: computational modeling; laser-induced deposition; metal alloy nanoparticles; microscopic Müller matrix measurement technique; orthorhombic carbon

Investigating the Surface of Nanoparticles by Second Harmonic Generation - Wunderlich, Sarina; Peschel, Ulf; Schürer, Benedikt; Peukert, Wolfgang (Conference on Lasers and Electro-Optics (CLEO)/Quantum Electronics and Laser Science Conference (QELS), 2010)
We investigate Second Harmonic Generation at the surface of nanoparticles both by modeling and experiment. We present an ab initio simulation method, which allows deducing surface properties as well as the nature of adsorbed molecules. (C) 2010 Optical Society of America

Investigation of noise sources down to the shot-noise limit in Yb-doped fiber amplifers for TMI investigations - Popp, Alexandra; Bock, Victor; Sedlmeir, Florian; Muller, Christian R.; Haarlammert, Nicoletta; Schreiber, Thomas; Marquardt, Christoph; Tunnermann, Andreas; Leuchs, Gerd (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Ytterbium-doped fiber laser amplifiers are known for their high single-pass gain and average powers up to the kilowatt range, while maintaining single-mode output. An upper limitation for the achievable output power is given by transverse mode instabilities (TMI). Due to the interference with higher order modes that create a thermally induced long period grating, chaotic power transfer happens above a certain threshold, which degrades the beam quality. It has been shown that this effect can be influenced by manipulating the grating strength itself. It has also been shown that a certain phase relation of the grating to the guided modes is necessary to efficiently transfer power or hinder the effect by phase disturbance [1]. A natural phase disturbance is given by noise, which is introduced by the pump or seed source in a fiber amplifer. In this contribution, we experimentally investigate the amount of intensity noise in a fiber-pre-amplifer, which is typically used in kW experiments and relate it to the fundamental shot noise limit (SNL). In the experiments, we used a single-frequency external cavity diode laser as a low noise source and amplify it by 30 dB from 10 mW to an output power of 10 W. This is a typical pre-amplifier configuration, before such sources can be amplified to the kW level. The fiber amplifier is a double-clad fiber with a 10/125 μm geometry, pumped by a wavelength stabilized pump diode at 976 nm via a monolithic pump coupler. In order to prevent stimulated Brillouin scattering, the seed laser is phase modulated by a combination of a sinusoid and white noise and thus broadened to 50 GHz linewidth. The noise measurements are done by balanced self-homodyne detection including optimized photodiode readout circuits spanning different frequency ranges. The recorded spectra are given in Fig. 1. The SNL was verified through an attenuation measurement for the subtracted detector signals. Finally, the measured excess noise values are fitted by their corresponding second-order polynomial power dependency and extrapolated to the full power of the amplifier. The seed source, phase modulator and fiber amplifier have been characterized in this setup separately to investigate their contributions. For the fiber amplifier, both co- and counter-pumping configuration, are analysed. Due to detector limitations, all given spectra are measured at an optical power in the mW regime corresponding to approx. 30 dB of attenuation in the amplifiers.
CRIS-Team Scopus Importer:2019-11-15

Investigation of phase singularities in the vicinity of small structures using a Linnik interference microscope - Leuchs, Gerd; et al. (Technisches Messen, 2000)
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.invest

Isotope shifts and hyperfine structure of the Fe I 372-nm resonance line - Krins, S.; Oppel, Steffen; Huet, N.; von Zanthier, Joachim; Bastin, T. (Physical Review A, 2009)
We report measurements of the isotope shifts of the 3d(6)4s(2) a (5)D(4)-3d(6)4s4p z (5)F(5)(o) Fe I resonance line at 372 nm between all four stable isotopes (54)Fe, (56)Fe, (57)Fe, and (58)Fe, as well as the complete hyperfine structure of that line for (57)Fe, the only stable isotope having a nonzero nuclear spin. The field and specific mass shift coefficients of the transition have been derived from the data, as well as the experimental value for the hyperfine structure magnetic dipole coupling constant A of the excited state of the transition in (57)Fe: A(3d(6)4s4p z (5)F(5)(o)) = 81.69(86) MHz. The measurements were carried out by means of high-resolution Doppler-free laser saturated absorption spectroscopy in a Fe-Ar hollow cathode discharge cell using both natural and enriched iron samples. The measured isotope shifts and hyperfine constants are reported with uncertainties at the percent leve

Ist 'Technisches Sehen' gleich 'Kamera + Computer'? - Häusler, Gerd; Leuchs, Gerd (Uni-Kurier-Magazin, 2003)
UnivIS-Import:2015-03-09:Pub.2003.nat.dphy.optik.1optik.isttec

Iterative correction of holographic lenses - Lindlein, Norbert; et al. (Proceedings of SPIE, 1994)
Holographic optical lens elements (HOEs) are volume grating in thick material such as dichromated gelatine (DCG) which suffer from the wavelength mismatch between the recording process and the practical application e.g., at laser diode wavelengths. Wavelength mismatch between recording and reconstruction is caused by the fact that the best recording materials are sensitive only in the blue region of the spectrum. The advantage of volume gratings (thickness 13 μm) is the large angle of deflection of the first diffraction order with a high diffraction efficiency. An optimized recording geometry using only spherical wave fronts allows on the one hand for the elimination of one of the third order aberrations (predominantly: astigmatism) or on the other hand for the fulfillment of the Bragg condition. To optimize the properties of holographic optical lens elements with one aspheric recording wave a kind of iterative procedure for the manufacturing is proposed. Each iteration consists of three different steps.
UnivIS-Import:2015-03-05:Pub.1994.nat.dphy.optik.1optik.iterat

Joint Surface Reconstruction and 4D Deformation Estimation from Sparse Data and Prior Knowledge for Marker-Less Respiratory Motion Tracking - Berkels, Benjamin; Bauer, Sebastian; Ettl, Svenja; Arold, Oliver; Hornegger, Joachim; Rumpf, Martin (Medical Physics, 2013)

Kalibrierung einer 3D Video Kamera - Häusler, Gerd; et al. (3.Optische Formerfassung, 1996)
UnivIS-Import:2015-04-16:Pub.1996.nat.dphy.optik.1optik.kalibr

Kalibrierung von optischen 3D-Sensoren - Häusler, Gerd; et al. (Optik, 1996)
UnivIS-Import:2015-03-05:Pub.1996.nat.dphy.optik.1optik.kalibr_2

Kalibrierverfahren von Sphären bei partieller Kohärenz - Lindlein, Norbert; Mantel, Klaus; Geist, Eduard; Hussendörfer, Benjamin (DGaO-Proceedings 2010 - http://www.dgao-proceedings.de - ISSN: 1614-8436, 2010)

Kelvin's chirality of optical beams - Nechayev, Sergey; Eismann, Jörg; Alaee, Rasoul; Karimi, Ebrahim; Boyd, Robert W.; Banzer, Peter (Physical Review A, 2021)
Geometrical chirality is a property of objects that describes a three-dimensional mirror-symmetry violation and therefore it requires a nonvanishing spatial extent. In contrary, optical chirality describes only the local handedness of electromagnetic fields and neglects the spatial geometrical structure of optical beams. In this Letter we put forward the physical significance of geometrical chirality of spatial structure of optical beams, which we term Kelvin's chirality. Furthermore, we report on an experiment revealing the coupling of Kelvin's chirality to optical chirality upon transmission of a focused beam through a planar medium. Our work emphasizes the importance of Kelvin's chirality in all light-matter interaction experiments involving structured light beams with spatially inhomogeneous phase and polarization distributions.
CRIS-Team Scopus Importer:2021-04-02

Kerker effect, superscattering, and scattering dark states in atomic antennas - Alaee, Rasoul; Safari, Akbar; Sandoghdar, Vahid; Boyd, Robert W. (Physical Review Research, 2020)
We study scattering phenomena such as the Kerker effect, superscattering, and scattering dark states in a subwavelength atomic antenna consisting of atoms with only electric dipole transitions. We show that an atomic antenna can exhibit arbitrarily large or small scattering cross sections depending on the geometry of the structure and the direction of the impinging light. We also demonstrate that atoms with only an electric dipole transition can exhibit a directional radiation pattern with zero backscattering when placed in a certain configuration. This is a special case of a phenomenon known as the Kerker effect, which typically occurs in the presence of both electric and magnetic transitions. Our findings open a pathway to design highly directional emitters, nonradiating sources, and highly scattering objects based on individually controlled atoms.
CRIS-Team WoS Importer:2021-01-29

Kerr-effect induced correlations of optical fiber solitons and the impact of phase control - Leuchs, Gerd; Glöckl, Oliver; Lorenz, Stefan; Marquardt, Christoph; Heersink, Joel; Korolkova, Natalia (Frontiers in Optics 2003, 2003)
Experiments are reported in which the quantum properties of intense optical pulses at 1.5 micrometer are controlled via their non-linear interaction with the optical fiber. Intense light pulses may exhibit non-classical features such as entanglement with application in quantum communication. The role of phase control will be discussed.<br

Kerr Enhancement of Optomechanics in Microresonators - Ghalanos, George N.; Silver, Jonathan M.; Zhang, Shuangyou; Del Bino, Leonardo; Bi, Toby; Del'Haye, Pascal (2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021, 2021)
When on-chip microresonators were first fabricated in 2005, it became apparent that these cavities exhibit op-tomechanical properties, evident by the parametric oscillation instability that was observed [1], [2]. This behaviour, resulting from radiation pressure, was then exploited for experiments involving cavity cooling [3], and coherent amplification in the form of a phonon laser [4].
CRIS-Team Scopus Importer:2021-10-29

Kerr-Nonlinearity-Induced Mode-Splitting in Optical Microresonators - Ghalanos, George N.; Silver, Jonathan M.; Del Bino, Leonardo; Moroney, Niall; Zhang, Shuangyou; Woodley, Michael T. M.; Svela, Andreas O.; Del'Haye, Pascal (Physical Review Letters, 2020)
The Kerr effect in optical microresonators plays an important role for integrated photonic devices and enables third harmonic generation, four-wave mixing, and the generation of microresonator-based frequency combs. Here we experimentally demonstrate that the Kerr nonlinearity can split ultra-high-Q microresonator resonances for two continuous-wave lasers. The resonance splitting is induced by self- and cross-phase modulation and counterintuitively enables two lasers at different wavelengths to be simultaneously resonant in the same microresonator mode. We develop a pump-probe spectroscopy scheme that allows us to measure power dependent resonance splittings of up to 35 cavity linewidths (corresponding to 52 MHz) at 10 mW of pump power. The required power to split the resonance by one cavity linewidth is only 286 mu W. In addition, we demonstrate threefold resonance splitting when taking into account four-wave mixing and two counterpropagating probe lasers. These Kerr splittings are of interest for applications that require two resonances at optically controlled offsets, e.g., for optomechanical coupling to phonon modes, optical memories, and precisely adjustable spectral filters.
CRIS-Team WoS Importer:2020-06-19

Kohärenzradar - ein 3D-Sensor im Genauigkeitsbereich von 1 µ - Häusler, Gerd; et al. (Technisches Messen, 2000)
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.kohren

Künstliche nanostrukturierte Polarisationselemente - Rothau, Sergej; Harder, Irina; Lindlein, Norbert (114. Jahrestagung der DGaO, 2013)

Label-free live-cell imaging with interferometric scattering microscopy: Confocal imaging and high-speed 3D single particle tracking - Küppers, Michelle; Kashkanova, Anna; Lühr, Jennifer; Albrecht, David; Schambony, Alexandra; Sandoghdar, Vahid (Optics InfoBase Conference Papers, 2020)
The combination of interferometric scattering microscopy (iSCAT) in wide-field and confocal detection reveals new prospects for the label-free visualization of subcellular processes and tracking of nanoscopic matter such as viruses, vesicles and lipid droplets.
CRIS-Team Scopus Importer:2020-10-02

Large-Area 3D Plasmonic Crescents with Tunable Chirality - Görlitzer, Eric; Mohammadi, Reza; Nechayev, Sergey; Banzer, Peter; Vogel, Nicolas (Advanced Optical Materials, 2019)
Chiral plasmonic nanostructures hold promise for enhanced chiral sensing and circular dichroism spectroscopy of chiral molecules. It is therefore of interest to fabricate chiral plasmonic nanostructures with tailored chiroptical properties over large areas with reasonable effort. Here, a colloidal lithography approach is used to produce macroscopic arrays of sub-micrometer 3D chiral plasmonic crescent structures over areas >1 cm 2 . The chirality originates from symmetry breaking by the introduction of a step within the crescent structure. This step is produced by an intermediate layer of silicon dioxide onto which the metal crescent structure is deposited. It is experimentally demonstrated that the chiroptical properties in such structures can be tailored by changing the position of the step within the crescent. These experiments are complemented by finite element simulations and the application of a multipole expansion to elucidate the physical origin of the circular dichroism of the crescent structures.
CRIS-Team Scopus Importer:2019-06-04
Keywords: chirality; colloidal lithography; multipole decomposition; plasmonics; split-ring resonator

Large field-of-view scanning white-light interferometers - Häusler, Gerd; et al. (18th Annual Meeting of American Society for Precision Engineering, 2003)
UnivIS-Import:2015-03-09:Pub.2003.nat.dphy.optik.1optik.largef

Laser-Induced Synthesis of Electrocatalytically Active Ag, Pt, and AgPt/Polyaniline Nanocomposites for Hydrogen Evolution Reactions - Vasileva, Anna A. A.; Mamonova, Daria V. V.; Petrov, Yuri V. V.; Kolesnikov, Ilya E. E.; Leuchs, Gerd; Manshina, Alina A. A. (Nanomaterials, 2023)
We present an efficient and easily implemented approach for creating stable electrocatalytically active nanocomposites based on polyaniline (PANI) with metal NPs. The approach combines in situ synthesis of polyaniline followed by laser-induced deposition (LID) of Ag, Pt, and AgPt NPs. The observed peculiarity of LID of PANI is the role of the substrate during the formation of multi-metallic nanoparticles (MNP). This allows us to solve the problem of losing catalytically active particles from the electrode's surface in electrochemical use. The synthesized PANI/Ag, PANI/Pt, and PANI/AgPt composites were studied with different techniques, such as SEM, EDX, Raman spectroscopy, and XPS. These suggested a mechanism for the formation of MNP on PANI. The MNP-PANI interaction was demonstrated, and the functionality of the nanocomposites was studied through the electrocatalysis of the hydrogen evolution reaction. The PANI/AgPt nanocomposites demonstrated both the best activity and the most stable metal component in this process. The suggested approach can be considered as universal, since it can be extended to the creation of electrocatalytically active nanocomposites with various mono- and multi-metallic NPs.
CRIS-Team WoS Importer:2023-01-27

Laser refrigeration of gas filled hollow-core fibres - Sommer, C.; Joly, Nicolas; Ritsch, H.; Genes, C. (AIP Advances, 2019)
We evaluate prospects, performance and temperature limits of a new approach to macroscopic scale laser refrigeration. The considered refrigeration device is based on exciplex-mediated frequency up-conversion inside hollow-core fibers pressurized with a dopant - buffer gas mixture. Exciplexes are excited molecular states formed by two atoms (dopant and buffer) which do not form a molecule in the ground state but exhibit bound states for electronically excited states. The cooling cycle consists of absorption of laser photons during atomic collisions inducing light assisted exciplex formation followed by blue-shifted spontaneous emission on the atomic line of the bare dopant atoms after molecular separation. This process, closely related to reversing the gain mechanism in excimer lasers, allows for a large fraction of collision energy to be extracted in each cycle. The hollow-core fiber plays a crucial role as it allows for strong light-matter interactions over a long distance, which maximizes the cooling rate per unit volume and the cooling efficiency per injected photon while limiting re-absorption of spontaneously emitted photons channeled into unguided radiation modes. Using quantum optical rate equations and refined dynamical simulations we derive general conditions for efficient cooling of both the gas and subsequently of the surrounding solid state environment. Our analytical approach is applicable to any specific exciplex system considered and reveals the shape of the exciplex potential landscapes as well as the density of the dopant as crucial tuning knobs. The derived scaling laws allow for the identification of optimal exciplex characteristics that help to choose suitable gas mixtures that maximize the refrigeration efficiency for specific applications.
CRIS-Team Scopus Importer:2019-10-29

Laser triangulation: Fundamental uncertainty in distance measurement - Häusler, Gerd; et al. (Applied Optics, 1994)
This paper presents a theoretical discussion of the fundamental uncertainty of distance measurements by caused by speckle during laser triangulation. Other contributing factors are the observation aperture and the angle of triangulation. For short-range macroscopic applications this uncertainty is in the range of couple micrometers to more than 10 μm, and is independent of the size of the spot size projected, provided this spot is larger than the observed speckle. Low temporal illumination reduces the uncertainty by more than twice for rough surfaces, although N-fold loss of lateral resolution results from an N-fold improvement in the distance uncertainty.
UnivIS-Import:2015-03-05:Pub.1994.nat.dphy.optik.1optik.lasert

Lateral Shearing Interferometer for Phase Shift Mask Measurement at 193 nm - Lindlein, Norbert; et al. (Proceedings of SPIE, 2002)
The physical limits of optical lithography are mainly determined by the aperture of the mask projection system and the wavelength of the light. In addition to the wavelength shift to the deep UV the application of special techniques to improve the processing window are required. This has furthered the application of the phase shift mask as a lithography tool. The generation of the exact intensity distribution needed in the plane of the wafer strongly depends on the accuracy of the phase shift introduced by the phase shift mask. However, one difficult issue is the reliable measurement of the phase shift introduced by the phase mask at the working wavelength. This is of course mainly due to the lack of suitable and simple interferometric devices for the deep-UV-region - here 193 nm. We propose the use of a diffractive shearing interferometer as a way out. By combining two Ronchi-phase gratings it is possible to produce shear and phase shifts for the evaluation of the fringe patterns simply by axial and lateral shifts of the phase gratings relative to each other. Since the excimer laser emits spatially partial coherent light only the coherence issue is one of the physical problems dealt with in our experiments. The state of the art of our experiments so far reached will be presented.
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.latera
Keywords: 193 nm lithography; Complex degree of coherence; Phase measurement; Phase shift mask; Shearing interferometer

Lateral Shearing Interferometry with Simultaneous Detection of both Gradient Fields on a Common Detector Grid - Lindlein, Norbert; et al. (6th International Workshop on Advanced Optical Metrology, Fringe 2009, 2009)

Lateral spin transport in paraxial beams of light - Neugebauer, Martin; Grosche, Simon; Rothau, Sergej; Leuchs, Gerd; Banzer, Peter (Optics Letters, 2016)
We investigate the lateral transport of (longitudinal) spin angular momentum in a special polarization tailored light beam composed of a superposition of a y-polarized zero-order and an x-polarized first-order Hermite-Gaussian mode. This phenomenon is linked to the relative Gouy phase shift between the individual modes upon propagation, but can also be interpreted as a geometric phase effect. Experimentally, we demonstrate the implementation of such a mode and measure the spin density upon propagation.

Lattice-plasmon-induced asymmetric transmission in two-dimensional chiral arrays - Apurv Chaitanya, N.; Butt, Muhammad; Reshef, O.; Boyd, Robert W.; Banzer, Peter; De Leon, Israel (APL Photonics, 2022)
Asymmetric transmission - direction-selective electromagnetic transmission between two ports - is a phenomenon exhibited by two-dimensional chiral systems. The possibility of exploiting this phenomenon in chiral metasurfaces opens exciting possibilities for applications such as optical isolation and routing without external magnetic fields. This work investigates optical asymmetric transmission in chiral plasmonic metasurfaces supporting lattice plasmon modes and unveils its physical origins. We show numerically and experimentally that asymmetric transmission is caused by an unbalanced excitation of such lattice modes by circularly polarized light of opposite handedness. The excitation efficiencies of the lattice modes, and hence, the strength of the asymmetric transmission, are controlled by engineering the in-plane scattering of the individual plasmonic nanoparticles such that the maximum scattering imbalance occurs along one of the in-plane diffraction orders of the metasurface. Furthermore, we show that only the nonzero diffraction orders contribute to this effect. By highlighting the role of the localized plasmon modes supported by the nanoparticle and their radiative coupling to the lattice structure, our study provides a guideline for designing metasurfaces with asymmetric transmission enabled by lattice plasmons.
CRIS-Team Scopus Importer:2022-02-04

Lectures on Quantum Information - Leuchs, Gerd; et al. (Wiley-VCH Verlag GmbH & Co KGaA, 2006)
UnivIS-Import:2015-04-02:Pub.2006.nat.dphy.optik.1optik.lectur

Lectures on Quantum Information - Leuchs, Gerd; et al. (Wiley-VCH Verlag GmbH & Co KGaA, 2006)
UnivIS-Import:2015-05-08:Pub.2006.nat.dphy.optik.1optik.contin_6

Light in curved two-dimensional space - Schultheiß, Vincent; Schultheiß, Vincent; Batz, Sascha; Peschel, Ulf (Advances in Physics: X, 2020)
The extrinsic and intrinsic curvature of a two-dimensional wave-guide influences wave propagation therein. While this can already be apprehended from a geometric point of view in terms of geodesics generalizing straight lines as the shortest distance between any two points, in wave optics interference phenomena strongly govern the field evolution, too. Radii of curvature in the order of the wavelength of light modify the local effective refractive index by altering the mode profile. Macroscopic radii only influence light propagation for non-vanishing intrinsic (or Gaussian) curvature. A positive Gaussian curvature leads to refocusing and thus an imaging behavior, whereas negative Gaussian curvature forces the field profile to diverge exponentially. These effects can be explained by an effective transverse potential acting on the electromagnetic field distribution's envelope. This can also be extended to nonlinear beam propagation. In this review paper we give a thorough introduction to differential geometry in two-dimensional manifolds and its incorporation with Maxwell's equations. We report on first fundamental experiments in this newly emerging field, which may lead to applications in integrated optical circuits. The dose conceptual analogy to phenomena in four-dimensional spacetime with constant curvature as well as toy-models of the Schwarzschild metric and a wormhole topology are also discussed.
CRIS-Team WoS Importer:2020-07-17

Light-matter interaction in free space - Leuchs, Gerd; Sondermann, Markus (Journal of Modern Optics, 2013)
We review recent experimental advances in the field of efficient coupling of single atoms and light in free space. Furthermore, a comparison of efficient free space coupling and strong coupling in cavity quantum electrodynamics (QED) is given. Free space coupling does not allow for observing oscillatory exchange between the light field and the atom which is the characteristic feature of strong coupling in cavity QED. Like cavity QED, free space QED does, however, offer full switching of the light field, a 180° phase shift conditional on the presence of a single atom as well as 100% absorption probability of a single photon by a single atom. Furthermore, free space cavity QED comprises the interaction with a continuum of modes. © 2013 Copyright Taylor and Francis Group, LLC.
Keywords: atom-photon coupling; free space QED; strong focussing

Light propagation in a GRIN microlens with gain or loss and comparison with lossless case - Lindlein, Norbert; et al. (Micro-Optics, VCSELs, and Photonic Interconnects II: Fabrication, Packaging, and Integration, 2006)
The correspondence between the linear integral transform and the ray-transfer matrix of a diffraction-free first-order optical system is used to describe the ray trajectory and to study the point spread function (PSF) in an active GRIN microlens characterized by a complex refractive index. The results show that the active microlens is regarded as a lossless microlens with a Gaussian mask induced by the complex refractive index. Comparison between light propagation effects in passive and active GRIN microlens is outlined.
Keywords: Active material; GRIN optics; PSF; Ray-tracing

Limits of Optical Range Sensors and How to Exploit Them - Häusler, Gerd; et al. (Trends in Optics and Phototonics, 1999)
UnivIS-Import:2015-04-20:Pub.1999.nat.dphy.optik.1optik.limits

Linear and nonlinear experiments in PT-Symmetric photonic mesh lattices - Wimmer, Martin; Christodoulides, Demetrios; Peschel, Ulf (Parity-time Symmetry and Its Applications, 2018)
Photonic mesh lattices provide a versatile experimental platform for studying light propagation in a discrete environment. By using standard telecommunication equipment it is possible to influence the evolution of light by actively modulating its amplitude and phase. Fiber components thus offer a ready to use solution for creating a PT -symmetric optical network. Here, we analyze two classes of PT -symmetric networks: Those with local PT symmetry fulfilling the conditions of PT symmetry in each time step but not globally and those with global PT symmetry providing completely real eigenvalues. We investigate light propagation in these dissipative media in the linear and nonlinear regime and discuss nonlinear localization as well as the formation of soliton. Furthermore, Bloch oscillations are induced by an external phase modulation and are found to restore pseudo-Hermitian propagation.
CRIS-Team Scopus Importer:2023-04-20

Localization and registration of 3D-objects in space - where are the limits? - Häusler, Gerd; et al. (Applied Optics, 2001)
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.optik.1optik.locali

Localized temperature and pressure measurements inside CS2-filled fiber using stimulated Brillouin scattering - Popp, Alexandra; Geilen, Andreas; Walter, Daniel; Chemnitz, Mario; Junaid, Saher; Poulton, Christopher G.; Marquardt, Christoph; Schmidt, Markus A.; Stiller, Birgit (2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021, 2021)
Liquid-core fibers are a versatile platform for nonlinear light-matter interactions, combining highly nonlinear materials like carbon disulfide (CS 2 ) or nitrobenzene with the confinement and long interaction length of optical fibers. While there is only minor influence of strain inside the fiber core due to the liquid phase, pressure effects have a dominant role depending on the thermodynamic regime and filling of the fiber core [1]. In our experiments we use Brillouin Optical Correlation Domain Analysis (BOCDA) to create a localized Brillouin response [2]. Due to the associated refractive index change, this response is strain, pressure and temperature dependent. While the discrimination of strain and temperature effects in silica fibers is complicated due to the combined Brillouin response [3] , CS 2 filled fibers have the advantage of thermo- and piezo-optical coefficients with different signs. While the thermo-optic coefficient is negative, resulting in a downshifted acoustic response for higher temperature, the piezo-optic coefficient is positive, resulting in an upshifted Brillouin frequency for increased pressure. To investigate the response of the CS 2 , we heated different parts of the 60cm liquid-core fiber on a hotplate up to a temperature of 135 C while measuring the distributed Brillouin response with a resolution of 4cm.
CRIS-Team Scopus Importer:2021-10-29

Localizing Eavesdroppers Inside a Quantum Channel Using Stimulated Brillouin Scattering - Popp, Alexandra; Stiller, Birgit; Marquardt, Christoph (2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2023)
While modern communication systems pose a high standard of security using state-of-the-art encryption techniques based on computational hardness problems, quantum key distribution (QKD) offers a unique advantage using the laws of quantum mechanics. A secret key is shared between two parties, using quantum states of light over a quantum channel. Due to the quantum nature of the states, any interception or other way of eavesdropping will manifest in the distortion of the quantum state resulting in a change of accessible parameters. Whenever such a change of parameters is noticed, the shared key is marked unsecure and hashed down largely or, in the worst case, discarded.<br
Keywords: Quantum computing; Quantum channels; Europe; Quantum state; Distortion; Quantum key distribution; Encryption

Local sampling of the SU(1,1) Wigner function - Fabre, Nicolas; Klimov, Andrei B.; Leuchs, Gerd; Sánchez-Soto, Luis L. (AVS Quantum Science, 2023)
Despite its indisputable merits, the Wigner phase-space formulation has not been widely explored for systems with SU(1,1) symmetry, as a simple operational definition of the Wigner function has proved elusive in this case. We capitalize on unique properties of the parity operator, to derive in a consistent way a bona fide SU(1,1) Wigner function that faithfully parallels the structure of its continuous-variable counterpart. We propose an optical scheme, involving a squeezer and photon-number-resolving detectors, that allows for direct point-by-point sampling of that Wigner function. This provides an adequate framework to represent SU(1,1) states satisfactorily.
CRIS-Team Scopus Importer:2023-03-03

Local wave fronts at diffractive elements - Lindlein, Norbert; et al. (Journal of the Optical Society of America A: Optics and Image Science, and Vision, 1993)
Equations for calculating the principal curvatures and principal directions of local wave fronts in an optical system that consists of diffractive curved or plane surfaces between isotropic and homogeneous media are presented. The equations for refractive and reflecting surfaces are obtained as special cases of the equations for diffractive surfaces. This method is a kind of generalized ray tracing and permits an easy determination of the position of the local focus or the position and direction of the local focal lines in the case of local astigmatism; it must be emphasized that elements and systems with spherical aberration or coma also have local astigmatism. © 1993 Optical Society of America.

Long distance free-space propagation of light carrying orbital angular momentum - Lavery, Martin P.J.; Peuntinger, Christian; Günthner, Kevin; Bauer, Thomas; Banzer, Peter; Elser, Dominique Alexander; Boyd, Robert W.; Padgett, Miles J.; Marquardt, Christoph; Leuchs, Gerd (Optics InfoBase Conference Papers, 2016)
We present analysis of the technical challenges facing deployment of longdistance free-space links employing orbital angular momentum multiplexing. Our analysis indicates atmospheric mitigation techniques, and modal purity are important consideration for system design.
CRIS-Team Scopus Importer:2022-06-05

Long-distance laser propulsion and deformation- monitoring of cells in optofluidic photonic crystal fiber - Unterkofler, Sarah; Garbos, Martin K.; Euser, Tijmen G.; Russell, Philip St. John (Journal of Biophotonics, 2013)
We introduce a unique method for laser-propelling individual cells over distances of 10s of cm through stationary liquid in a microfluidic channel. This is achieved by using liquid-filled hollow-core photonic crystal fiber (HC-PCF). HC-PCF provides low-loss light guidance in a well-defined single mode, resulting in highly uniform optical trapping and propulsive forces in the core which at the same time acts as a microfluidic channel. Cells are trapped laterally at the center of the core, typically several microns away from the glass interface, which eliminates adherence effects and external perturbations. During propagation, the velocity of the cells is conveniently monitored using a non-imaging Doppler velocimetry technique. Dynamic changes in velocity at constant optical powers up to 350 mW indicate stress-induced changes in the shape of the cells, which is confirmed by bright-field microscopy. Our results suggest that HC-PCF will be useful as a new tool for the study of single-cell biomechanics.
EAM Import::2019-03-12

Lossless propagation of magnetic dipole excitations on chains of dielectric particles with high refractive index - Zhuromskyy, Oleksandr; Peschel, Ulf (Physical Review B, 2014)
Lossless propagation of longitudinal magnetic dipole waves along chains of high-index subwavelength particles is predicted for a narrow frequency range around the magnetic Mie resonance of the individual particles. Mathematical analogies between dipole and magnetoinductive waves are used to reduce back-reflections thus improving the power transfer efficiency of respective particle waveguides. The proposed technique can be used to optimize the propagation of even more complex particle-based configurations.
EAM Import::2019-03-12

Lower bounds for the time-bandwidth product of a single-photon pulse - Averchenko, V.; Reiß, D. A.; Sych, D.; Leuchs, Gerd (Physica Scripta, 2020)
Two complementary properties, such as frequency and duration of a pulse, cannot be precisely measured simultaneously. The lower bound on the time-bandwidth product, known also as uncertainty relation, plays a very important role in quantum theory. In this work, we consider single-photon pulses with arbitrary temporal and spectral profiles, and derive a lower bound for the single-photon time-bandwidth product. We investigate how this bound depends on the modal purity, the single-mode fidelity, and the effective number of modes. Our results can be used to solve the inverse problem, namely, to estimate characteristics of the single-photon pulse based on the time-bandwidth product obtained from temporal and spectral measurements of the pulse.
CRIS-Team Scopus Importer:2020-03-06

Low-loss single-mode negatively curved square-core hollow fibers - Chen, Yang; Saleh, Mohammed F.; Joly, Nicolas; Biancalana, Fabio (Optics Letters, 2017)
We introduce a novel design of anti-resonant fibers with negative-curvature square cores to be employed in 1.55 and 2.94 mu m transmission bands. The fibers have low losses and single-mode operation via optimizing the negative curvature of the guiding walls. The first proposed fiber shows a broadband transmission window spanning 0.9-1.7 mu m, with losses of 0.025 and 0.056 dB/m at 1.064 and 1.55 mu m, respectively. The second proposed fiber has approximately a 0.023 dB/m guiding loss at 2.94 mu m with a small cross-sectional area, useful for laser micromachining applications. (C) 2017 Optical Society of America

Low-threshold optical parametric oscillations in a whispering gallery mode resonator - Fuerst, J. U.; Strekalov, D. V.; Elser, Dominique Alexander; Aiello, Andrea; Andersen, U. L.; Marquardt, Christoph; Leuchs, Gerd (Physical Review Letters, 2010)
In whispering gallery mode (WGM) resonator light is guided by continuous total internal reflection along a curved surface. Fabricating such resonators from an optically nonlinear material one takes advantage of their exceptionally high quality factors and small mode volumes to achieve extremely efficient optical frequency conversion. Our analysis of the phase-matching conditions for optical parametric down-conversion (PDC) in a spherical WGM resonator shows their direct relation to the sum rules for photons' angular momenta and predicts a very low parametric oscillation threshold. We realized such an optical parametric oscillator (OPO) based on naturally phase-matched PDC in lithium niobate. We demonstrated a single-mode, strongly nondegenerate OPO with a threshold of 6.7μW and linewidth under 10 MHz. This work demonstrates the remarkable capabilities of WGM-based OPOs. © 2010 The American Physical Society.
CRIS-Team Scopus Importer:2022-06-05

Making Diffraction Limited Refractive Microlenses of Spherical and Elliptical Form - Lindlein, Norbert; et al. (EOS Topical Meetings Digest Series, 1997)
UnivIS-Import:2015-03-05:Pub.1997.nat.dphy.optik.1optik.making

Management of spontaneous enophthalmos due to silent sinus syndrome: a case report - Nkenke, Emeka; Alexiou, Christoph; Iro, Heinrich; Amann, Kerstin Ute; Kirchner, Thomas; Häusler, Gerd; Neukam, Friedrich Wilhelm; Holbach, Benedict (International Journal of Oral and Maxillofacial Surgery, 2005)
UnivIS-Import:2015-04-14:Pub.2005.nat.dphy.optik.1optik.manage

Manufacturing of Polymer Optical Waveguides for 3D-Opto-MID: Review of the OPTAVER Process - Hamjah, Mohd Khairulamzari; Zeitler, Jochen Tobias; Eiche, Yannic; Lorenz, Lukas; Backhaus, Carsten; Hoffmann, Gerd Albert; Wienke, Alexander; Kaierle, Stefan; Overmeyer, Ludger; Lindlein, Norbert; Bock, Karlheinz; Franke, Jörg (2021 14th International Congress: Molded Interconnect Devices, MID 2021 - Proceedings, 2021)
In order to meet the increasing demand for data transmission over short distances of up to 100 m, the Optical Assembly and Connection Technology for ComponentIntegrated Bus Systems (OPTAVER) research group, funded by the German Research Foundation (DFG), developed a process for the additive manufacturing of three-dimensional optical waveguides. The research group focuses on design and modeling, simulation, and manufacturing polymer optical waveguides to produce 3D-Opto-Mechatronic-Integrated Devices (3D-Opto-MID). Inside 3D-Opto-MID, an optical coupler is presented based on an asymmetrical coupling principle. This paper reviews the entire process chain and the corresponding research results of the OPTAVER process.
CRIS-Team Scopus Importer:2021-03-26
Keywords: 3D-Opto-MID; aerosol jet printing; asymmetrical optical bus coupling; flexographic printing; functionalization; printed multimode waveguides; Raytracing; wave propagation method

Many-Body Quantum Dynamics of Polarization Squeezing in Optical Fibers - Leuchs, Gerd; et al. (Physical Review Letters, 2006)
We report new experiments that test quantum dynamical predictions of polarization squeezing for ultrashort photonic pulses in a birefringent fiber, including all relevant dissipative effects. This exponentially complex many-body problem is solved by means of a stochastic phase-space method. The squeezing is calculated and compared to experimental data, resulting in excellent quantitative agreement. From the simulations, we identify the physical limits to quantum noise reduction in optical fibers. The research represents a significant experimental test of first-principles time-domain quantum dynamics in a one-dimensional interacting Bose gas coupled to dissipative reservoirs. © 2006 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2006.nat.dphy.optik.1optik.manybo

Marker-less reconstruction of dense 4-D surface motion fields using active laser triangulation for respiratory motion management - Bauer, Sebastian; Berkels, Benjamin; Ettl, Svenja; Arold, Oliver; Hornegger, Joachim; Rumpf, Martin (15th International Conference, Nice, France, October 1-5, 2012, Proceedings, Part I, 2012)
To manage respiratory motion in image-guided interventions a novel sparse-to-dense registration approach is presented. We apply an emerging laser-based active triangulation (AT) sensor that delivers sparse but highly accurate 3-D measurements in real-time. These sparse position measurements are registered with a dense reference surface extracted from planning data. Thereby a dense displacement field is reconstructed which describes the 4-D deformation of the complete patient body surface and recovers a multi-dimensional respiratory signal for application in respiratory motion management. The method is validated on real data from an AT prototype and synthetic data sampled from dense surface scans acquired with a structured light scanner. In a study on 16 subjects, the proposed algorithm achieved a mean reconstruction accuracy of +/- 0.22 mm w.r.t. ground truth data.
UnivIS-Import:2015-04-16:Pub.2012.tech.IMMD.IMMD5.marker

M-ary phase shift keying receiver beating the standard quantum limit for any signal power - Müller, Christian R.; Leven, Andreas; Bülow, Henning; Schmalen, Laurent; Leuchs, Gerd; Marquardt, Christoph (European Conference on Optical Communication, ECOC, 2014)
We analyze a novel quantum receiver for M-ary phase-shift keyed signals that outperforms the standard quantum limit for any signal power. We provide a detailed analysis of its robustness against realistic imperfections and discuss the achievable mutual information.
CRIS-Team Scopus Importer:2022-06-05

Mass transfer of organic substances in supercritical carbon dioxide - Hu, Miao; Benning, Rainer; Ertunc, Özgür; Neukam, Johannes; Bielke, Thorsten; Delgado, Antonio; Nercissian, Vanusch; Berger, Andreas (Journal of Physics : Conference Series, 2011)
In this work special attention is paid on the direct visualization of the diffusion process of oil droplets in supercritical carbon dioxide as well as better characterization of the process by quantitatively evaluating the important parameter - the diffusion coefficients obtained with a shearing interferometer. Experiments are also to be carried out under microgravity to improve the experiment condition where the influence of gravity-driven convection that usually dominates the transport process is minimized.
UnivIS-Import:2015-03-09:Pub.2011.tech.ITC.stmmec.masstr_3

Mass transfer of organic substances in supercritical carbon dioxide - Hu, Miao; Benning, Rainer; Ertunc, Özgür; Delgado, Antonio; Nercissian, Vanusch; Berger, Andreas (Defect and Diffusion Forum, 2012)
In this work special attention is paid on the direct visualization of the diffusion process of oil droplets in supercritical carbon dioxide as well as a better characterization of the process by quantitative evaluation of the diffusion coefficients obtained with a shearing interferometer. Experiments are also to be carried out under microgravity in to improve the experiment condition where the influence of gravity-driven convection that usually dominates the transport process is minimized. © (2012) Trans Tech Publications.
UnivIS-Import:2015-04-16:Pub.2012.tech.ITC.stmmec.masstr
Keywords: Diffusion coefficient; Microgravity; Shearing-interferometer; Supercritical carbon dioxide

Matrix stiffness mechanosensing modulates the expression and distribution of transcription factors in Schwann cells - Rosso, Gonzalo; Wehner, Daniel; Schweitzer, Christine; Sock, Elisabeth; Guck, Jochen; Shahin, Victor; Möllmert, Stephanie (Bioengineering & Translational Medicine, 2021)
After peripheral nerve injury, mature Schwann cells (SCs) de-differentiate and undergo cell reprogramming to convert into a specialized cell repair phenotype that promotes nerve regeneration. Reprogramming of SCs into the repair phenotype is tightly controlled at the genome level and includes downregulation of pro-myelinating genes and activation of nerve repair-associated genes. Nerve injuries induce not only biochemical but also mechanical changes in the tissue architecture which impact SCs. Recently, we showed that SCs mechanically sense the stiffness of the extracellular matrix and that SC mechanosensitivity modulates their morphology and migratory behavior. Here, we explore the expression levels of key transcription factors and myelin-associated genes in SCs, and the outgrowth of primary dorsal root ganglion (DRG) neurites, in response to changes in the stiffness of generated matrices. The selected stiffness range matches the physiological conditions of both utilized cell types as determined in our previous investigations. We find that stiffer matrices induce upregulation of the expression of transcription factors Sox2, Oct6, and Krox20, and concomitantly reduce the expression of the repair-associated transcription factor c-Jun, suggesting a link between SC substrate mechanosensing and gene expression regulation. Likewise, DRG neurite outgrowth correlates with substrate stiffness. The remarkable intrinsic physiological plasticity of SCs, and the mechanosensitivity of SCs and neurites, may be exploited in the design of bioengineered scaffolds that promote nerve regeneration upon injury.
CRIS-Team Scopus Importer:2021-10-01
Keywords: cell plasticity; extracellular matrix stiffness; mechanosensing; nerve regeneration; neuron; Schwann cell

Maximization of the optical intra-cavity power of whispering-gallery mode resonators via coupling prism - Santamaría-Botello, G.A.; Garcia Munoz, Luis Enrique; Sedlmeir, Florian; Preu, Sascha; Preu, Sascha; Segovia-Vargas, Daniel; Atia Abdalmalak, K.; Llorente Romano, S.; García Lampérez, A.; Malzer, Stefan; Döhler, Gottfried; Schwefel, Harald; et al. (Optics Express, 2016)
In this paper, a detailed description of the optical coupling into a Whispering Gallery Mode (WGM) resonator through a prism via frustrated total internal reflection (FTIR) is presented. The problem is modeled as three media with planar interfaces and closed expressions for FTIR are given. Then, the curvature of the resonator is taken into account and the mode overlap is theoretically studied. A new analytical expression giving the optimal geometry of a disc-shaped or ring-shaped resonator for maximizing the intra-cavity circulating power is presented. Such expression takes into consideration the spatial distribution of the WGM at the surface of the resonator, thus being more accurate than the currently used expressions. It also takes into account the geometry of the prism. It is shown an improvement in the geometry values used with the current expressions of about 30%. The reason why the pump laser signal can be seen in experiments under critical coupling is explained on this basis. Then, the conditions required for exciting the highest possible optical power inside the resonator are obtained. The aim is to achieve a highly-efficient up-conversion of a THz signal into the optical domain via the second-order nonlinearity of the resonator material. (C) 2016 Optical Society of America

Maximizing the electric field strength in the foci of high numerical aperture optics - Sondermann, Markus; Lindlein, Norbert; Leuchs, Gerd (arXiv, 2008)

Measurement devices with and for micro-optics at the university of Erlangen - Lindlein, Norbert; et al. (Proceedings of SPIE, 1998)
Several devices for the measurement of micro-optical elements will be presented. These are a Mach-Zehnder interference microscope for the measurement of the wave aberrations of microlenses in transmission using a HeNe laser (633nm wavelength) and a shearing interferometer for the measurement of microlenses in transmission in the near infrared (1319nm). This shearing interferometer uses two Ronchi gratings to provide a lateral shear and is therefore very compact and stable. We also describe a Twyman-Green interference microscope for the measurement of (nearly) spherical surfaces in reflection using partially coherent illumination. Microlenses can be also used to build measurement devices for micro- and macro-optics. We will present a Shack-Hartmann wavefront sensor with microlenses for the measurement of quite arbitrary wavefronts and a confocal set-up which uses an array of microlenses and stops to provide a confocal measurement without a lateral scanning of the object. This confocal setup can be used to measure the surface profile of micro-optical structures like gratings or microlenses.
UnivIS-Import:2015-03-05:Pub.1998.nat.dphy.optik.1optik.measur
Keywords: Confocal microscope; Mach-Zehnder interferometer; Measurement devices for micro-optical elements; Microlenses; Shack-Hartmann wavefront sensor; Shearing interferometer; Twyman-Green interferometer

Measurement of atmospheric neutrino mixing with improved IceCube DeepCore calibration and data processing - Abbasi, R.; Ackermann, M.; Adams, J.; Agarwalla, S. K.; Aguilar, J. A.; Ahlers, M.; Alameddine, J. M.; Amin, N. M.; Andeen, K.; Anton, Gisela; Argüelles, C.; Ashida, Y.; et al. (Physical Review D, 2023)
We describe a new data sample of IceCube DeepCore and report on the latest measurement of atmospheric neutrino oscillations obtained with data recorded between 2011-2019. The sample includes significant improvements in data calibration, detector simulation, and data processing, and the analysis benefits from a sophisticated treatment of systematic uncertainties, with significantly greater level of detail since our last study. By measuring the relative fluxes of neutrino flavors as a function of their reconstructed energies and arrival directions we constrain the atmospheric neutrino mixing parameters to be sin2θ23=0.51±0.05 and Δm322=2.41±0.07×10-3 eV2, assuming a normal mass ordering. The errors include both statistical and systematic uncertainties. The resulting 40% reduction in the error of both parameters with respect to our previous result makes this the most precise measurement of oscillation parameters using atmospheric neutrinos. Our results are also compatible and complementary to those obtained using neutrino beams from accelerators, which are obtained at lower neutrino energies and are subject to different sources of uncertainties.
CRIS-Team Scopus Importer:2023-08-25

Measurement of Minute Liquid Volumes of Chiral Molecules Using In-Fiber Polarimetry - Schorn, Florian; Essert, Arabella; Zhong, Yu; Abdullayev, Sahib; Castiglione, Kathrin; Haumann, Marco; Joly, Nicolas (Analytical Chemistry, 2023)

Measurement of TLR-induced macrophage spreading by automated image analysis: Differential role of Myd88 and MAPK in early and late responses - Wenzel, Jens; Held, Christian; Palmisano, Ralf; Teufel, S.; David, Jean Pierre; Wittenberg, Thomas; Lang, Roland (Frontiers in Physiology, 2011)
Sensing of infectious danger by toll-like receptors (TLRs) on macrophages causes not only a reprogramming of the transcriptome but also changes in the cytoskeleton important for cell spreading and motility. Since manual determination of cell contact areas from fluo-, rescence micrographs is very time-consuming and prone to bias, we have developed and tested algorithms for automated measurement of macrophage spreading. The two-step method combines identification of cells by nuclear staining with DAPI and cell surface staining of the integrin CD11b. Automated image analysis correlated very well with manual annotation in resting macrophages and early after stimulation, whereas at later time points the automated cell segmentation algorithm and manual annotation showed slightly larger variation. The method was applied to investigate the impact of genetic or pharmacological inhibition of known TLR signaling components. Deficiency in the adapter protein Myd88 strongly reduced spreading activity at the late time points, but had no impact early after LPS-stimulation. A similar effect was observed upon pharmacological inhibition of MEK1, the kinase activating the mitogen-activated protein kinases (MAPK) ERK1/2, indicating that ERK1/2 mediates Myd88-dependent macrophages spreading. In contrast, macrophages lacking the MAPK p38 were impaired in the initial spreading response but responded normally 8-24 h after stimulation. The dichotomy of p38 and ERK1/2 MAPK effects on early and late macrophage spreading raises the question which of the respective substrate proteins mediate(s) cytoskeletal remodeling and spreading. The automated measurement of cell spreading described here increases the objectivity and greatly reduces the time required for such investigations and is therefore expected to facilitate larger throughput analysis of macrophage spreading, e.g., in siRNA knockdown screens. © 2011 Wenzel, Held, Palmisano, Teufel, David, Wittenberg and Lang.

Measurements of the Electric Field of Zero-Point Optical Phonons in GaAs Quantum Wells Support the Urbach Rule for Zero-Temperature Lifetime Broadening - Bhattacharya, Rupak; Mondal, Richarj; Khatua, Pradip; Rudra, Alok; Kapon, Eli; Malzer, Stefan; Döhler, Gottfried; Pal, Bipul; Bansal, Bhavtosh (Physical Review Letters, 2015)
We study a specific type of lifetime broadening resulting in the well-known exponential "Urbach tail" density of states within the energy gap of an insulator. After establishing the frequency and temperature dependence of the Urbach edge in GaAs quantum wells, we show that the broadening due to the zero-point optical phonons is the fundamental limit to the Urbach slope in high-quality samples. In rough analogy with Welton's heuristic interpretation of the Lamb shift, the zero-temperature contribution to the Urbach slope can be thought of as arising from the electric field of the zero-point longitudinal-optical phonons. The value of this electric field is experimentally measured to be 3 kV cm(-1), in excellent agreement with the theoretical estimate.

Measuring higher-order photon correlations of faint quantum light: A short review - Laiho, K.; Dirmeier, T.; Schmidt, Marco; Reitzenstein, S.; Marquardt, Christoph (Physics Letters A, 2022)
Normalized correlation functions provide expedient means for determining the photon-number properties of light. These higher-order moments, also called the normalized factorial moments of photon number, can be utilized both in the fast state classification and in-depth state characterization. Further, non-classicality criteria have been derived based on their properties. Luckily, the measurement of the normalized higher-order moments is often loss-independent making their observation with lossy optical setups and imperfect detectors experimentally appealing. The normalized higher-order moments can for example be extracted from the photon-number distribution measured with a true photon-number-resolving detector or accessed directly via manifold coincidence counting in the spirit of the Hanbury Brown and Twiss experiment. Alternatively, they can be inferred via homodyne detection. Here, we provide an overview of different kind of state classification and characterization tasks that take use of normalized higher-order moments and consider different aspects in measuring them with free-traveling light. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
CRIS-Team WoS Importer:2022-05-20

Measuring Microwave Frequency Radiation at the Quantum Noise Limit - Eichler, Christopher (Conference on Mesoscopic Transport and Quantum Coherence 2017, 2017)
Electromagnetic radiation at microwave frequencies couples to a variety of systems ranging from electrical over mechanical to spin degrees of freedom. Engineered solid state devices facilitate thea controlled isolation of such modes on the single particle level and their strong interaction with individual microwave frequency photons. The sensitive detection and characterization of such photons is thus of central importance, which has propelled the development of quantum limited parametric amplifiers and more recently also photo detectors. In my talk I will discuss advances in the low noise amplification of microwave frequency radiation [1] and present their application in various experimental settings, including the sensitive detection of electron spin resonance [2], the fast and high fidelity readout of superconducting qubits [3], and the implementation of quantum variational algorithms [4]. [1] Eichler et al., Phys. Rev. Lett. 113, 110502 (2014); [2] Eichler et al., Phys. Rev. Lett. 118, 037701 (2017); [3] Walter et al., Phys. Rev. Applied 7, 054020 (2017); [4] Eichler et al., Phys. Rev. X 5, 041044 (2015).
Keywords: wwwqudev

Measuring microwave photon correlations with quantum limited amplifiers - Eichler, Christopher (invited talk by Yasunobu Nakamura, 2014)

Measuring the Kerr-nonlinearity of Ag in plasmonic nano-circuits - Kriesch, Arian; Pfeifer, Hannes; Burgos, Stanley P.; Ploss, Daniel; Banzer, Peter; Atwater, Harry A.; Peschel, Ulf (Nonlinear Optics 2013, 2013)
We observe nonlinear switching of ultrashort (600fs) laser pulses in subwavelength plasmonic nanocircuits. This allows us to experimentally determine the third-order nonlinear coefficient of silver.
EAM Import::2019-03-12

Measuring the modulus of the spatial coherence function using an error tolerant phase shifting algorithm and a continuous lateral shearing interferometer - Harder, Irina; Eisner, Martin; Voelkel, Reinhard; Rothau, Sergej; Schwider, Johannes; Schwider, Peter Mario (Optics Express, 2016)
The modulus of the degree of coherence can be derived from interference patterns either by using fringes and next neighbour operations or by using several interferograms produced through phase shifting. Here the latter approach will be followed by using a lateral shearing interferometer exploiting a diffractive grating wedge providing a linearly progressive shear. Phase shifting methods offer pixel-oriented evaluations but suffer from instabilities and drifts which is the reason for the derivation of an error immune algorithm. This algorithm will use five π/2-steps of the reference phase also for the calculation of the modulus of the coherence function.

Measuring the modulus of the spatial coherence function using an error tolerant phase shifting algorithm - Rothau, Sergej; Schwider, Johannes; Harder, Irina (117. Annual Meeting of the DGaO, 2016)

Measuring the temperature and heating rate of a single ion by imaging - Srivathsan, Bharath; Fischer, Martin; Alber, Lucas; Weber, Markus; Sondermann, Markus; Leuchs, Gerd (New Journal of Physics, 2019)

Mechanical properties of cell- and microgel bead-laden oxidized alginate-gelatin hydrogels - Distler, Thomas; Kretzschmar, Lena; Schneidereit, Dominik; Girardo, Salvatore; Goswami, Ruchi; Friedrich, Oliver; Detsch, Rainer; Guck, Jochen; Boccaccini, Aldo R.; Budday, Silvia (Biomaterials Science, 2021)
3D-printing technologies, such as biofabrication, capitalize on the homogeneous distribution and growth of cells inside biomaterial hydrogels, ultimately aiming to allow for cell differentiation, matrix remodeling, and functional tissue analogues. However, commonly, only the mechanical properties of the bioinks or matrix materials are assessed, while the detailed influence of cells on the resulting mechanical properties of hydro- gels remains insufficiently understood. Here, we investigate the properties of hydrogels containing cells and spherical PAAm microgel beads through multi-modal complex mechanical analyses in the small- and large- strain regimes. We evaluate the individual contributions of different filler concentrations and a non-fibrous oxi- dized alginate-gelatin hydrogel matrix on the overall mechanical behavior in compression, tension, and shear. Through material modeling, we quantify parameters that describe the highly nonlinear mechanical response of soft composite materials. Our results show that the stiffness significantly drops for cell- and bead concen- trations exceeding four million per milliliter hydrogel. In addition, hydrogels with high cell concentrations (≥6 mio ml−1) show more pronounced material nonlinearity for larger strains and faster stress relaxation. Our findings highlight cell concentration as a crucial parameter influencing the final hydrogel mechanics, with implications for microgel bead drug carrier-laden hydrogels, biofabrication, and tissue engineering.