Controlling the quantum properties of optical solitons in fibres - Leuchs, Gerd; et al. (Molecular Crystals and Liquid Crystals Science and Technology Section B: Nonlinear Optics, 2000)
Solitons in optical fibres are stable objects when described classically. The quantum properties,[1] however, change with propagation distance due to Kerr and Raman induced intrapulse correlations. It is demonstrated that spectral filters and interferometers can be used to control the quantum properties of 130 fs solitons. This lends to the generation of many photon states of the light field with non-classical noise reduction and quantum entanglement for application in quantum communication.
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.contro

Correlation measurement of squeezed light - Leuchs, Gerd; et al. (Physical Review A, 2009)
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.optik.1optik.correl

Corrupting coherence - ubquitous inthe metrologists daily life - Häusler, Gerd (Proc. of 3rd Topical Meeting onOptoelectronic Distance Measurement and Applications (ODIMAP III), 2001)
UnivIS-Import:2015-04-16:Pub.2001.nat.dphy.optik.1optik.corrup

Counterpropagating light in ring resonators: Switching fronts, plateaus, and oscillations - Campbell, Graeme N.; Zhang, Shuangyou; Del Bino, Leonardo; Del'Haye, Pascal; Oppo, Gian-Luca (Physical Review A, 2022)
We characterize the formation of robust stationary states formed by light plateaus separated by two local switching fronts in only one of two counterpropagating fields in ring resonators with normal dispersion. Such states are due to global cross coupling and allow for frequency combs to switch from one field to the other by simply tuning the input laser frequency. Exact expressions for the distance between fronts and for plateau powers are provided in excellent agreement with simulations. These demonstrate an unusual high degree of control over pulse and plateau duration in one of the fields upon changes of one of the input laser frequencies. We identify a wide parameter region in which light plateaus are self-starting and are the only stable solution. For certain values of the detunings we find multistable states of plateaus with switching fronts, slowly oscillating homogeneous states and nonoscillating homogeneous states of the counterpropagating fields. Robustness and multistability of these unusual single-field front solutions are provided in parameter ranges that are experimentally achievable in a wide variety of ring resonators.
CRIS-Team WoS Importer:2022-11-18

Covariance spectroscopy of molecular gases using fs pulse bursts created by modulational instability in gas-filled hollow-core fiber - Suresh, Mallika; Russell, Philip St. John; Tani, Francesco (Optics Express, 2020)
We present a technique that uses noisy broadband pulse bursts generated by modulational instability to probe nonlinear processes, including infrared-inactive Raman transitions, in molecular gases. These processes imprint correlations between different regions of the noisy spectrum, which can be detected by acquiring single shot spectra and calculating the Pearson correlation coefficient between the different frequency components. Numerical simulations verify the experimental measurements and are used to further understand the system and discuss methods to improve the signal strength and the spectral resolution of the technique.
CRIS-Team Scopus Importer:2020-11-20

Covariant constructive gravity: A step-by-step guide towards alternative theories of gravity - Alex, Nils; Reinhart, Tobias (Physical Review D, 2020)
We propose a step-by-step manual for the construction of alternative theories of gravity, perturbatively as well as nonperturbatively. The construction is guided by no more than two fundamental principles that we impose on the gravitational dynamics: invariance under spacetime diffeomorphisms and causal compatibility with given matter dynamics, provided that spacetime is additionally endowed with matter fields. The developed framework then guides the computation of the most general, alternative theory of gravity that is consistent with the two fundamental requirements. Utilizing this framework we recover the cosmological sector of general relativity solely from assuming that spacetime is a spatially homogeneous and isotropic metric manifold. On top of that, we explicitly test the perturbative framework by deriving the most general third-order expansion of a metric theory of gravity that is causally compatible with a Klein-Gordon scalar field. Thereby we recover the perturbative expansion of general relativity. To demonstrate how new physics emerges from our approach, we finally construct the most comprehensive third-order expansion of a theory of gravity that supports general (not necessarily Maxwellian) linear electrodynamics.
CRIS-Team WoS Importer:2020-04-24

Creating path entanglement and violating Bell inequalities by independent photon sources - Wiegner, Ralph; Thiel, Christoph; von Zanthier, Joachim; Agarwal, G. S. (Physics Letters A, 2010)
We demonstrate a novel approach of violating position-dependent Bell inequalities by photons emitted via independent single photon sources in free space. We trace this violation back to path entanglement created a posteriori by the selection of modes clue to the process of detection. (C) 2010 Elsevier B.V. All rights reserved.

Critical dynamics of an asymmetrically bidirectionally pumped optical microresonator - Silver, Jonathan M.; Grattan, Kenneth T.; Del'Haye, Pascal (Physical Review A, 2021)
An optical ring resonator with third-order, or Kerr, nonlinearity will exhibit symmetry breaking between the two counterpropagating circulating powers when pumped with sufficient power in both the clockwise and counterclockwise directions. This is due to the effects of self- and cross-phase modulation on the resonance frequencies in the two directions. The critical point of this symmetry breaking exhibits universal behaviors including divergent responsivity to external perturbations, critical slowing down, and scaling invariance. Here we derive a model for the critical dynamics of this system, first for a symmetrically pumped resonator and then for the general case of asymmetric pumping conditions and self- and cross-phase modulation coefficients. This theory not only provides a detailed understanding of the dynamical response of critical-point-enhanced optical gyroscopes and near-field sensors, but is also applicable to nonlinear critical points in a wide range of systems.
CRIS-Team Scopus Importer:2021-10-29

Cross-phase modulational instability of circularly polarized helical Bloch modes carrying optical vortices in a chiral three-core photonic crystal fiber - Roth, Paul; Frosz, Michael H.; Weise, Linda; Russell, Philip St. John; Wong, Gordon K. L. (Optics Letters, 2021)
We report the first, to the best of our knowledge, observation of cross-phase modulational instability (XPMI) of circularly polarized helical Bloch modes carrying optical vortices in a twisted photonic crystal fiber with a three-fold symmetric core, formed by spinning the fiber preform during the draw. When the fiber is pumped by a superposition of left-circular polarization (LCP) and right-circular polarization (RCP) modes, a pair of orthogonal circularly polarized sidebands of opposite topological charge is generated. When, on the other hand, a pure LCP (or RCP) mode is launched, the XPMI gain is zero, and no sidebands are seen. This observation has not been seen before in any system and is unique to chiral structures with N-fold rotational symmetry. The polarization state and topological charge of the generated sidebands are measured. By decomposing the helical Bloch modes into their azimuthal harmonics, we are able to deduce the selection rules for the appearance of modulational instability sidebands. We showed that the four waves in the nonlinear mixing process must exhibit the same set of azimuthal harmonic orders. (C) 2021 Optical Society of America
CRIS-Team WoS Importer:2021-02-12

Cross-phase Modulational Instability of Vortex Modes in a Twisted Three-Core Photonic Crystal Fibre - Wong, Gordon K. L.; Roth, Paul; Frosz, Michael H.; Russell, Philip St. John (2020 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR), 2020)
CRIS-Team WoS Importer:2021-06-11

Crowding competes with trapping to enhance interfacial diffusion - Cvitković, Mislav; Ghanti, Dipanwita; Raake, Niklas; Smith, Ana Sunčana (European Physical Journal Plus, 2022)
Diffusion of species on biological membranes or materials interfaces is expected to slow down with an increase in their density, but also due to their intermittent binding to functional moieties or surface-defects. These processes, known as crowding and trapping, respectively, occur simultaneously in a broad range of interfacial systems. However their combined effect on the diffusion coefficients was not studied hitherto. Here, we analytically calculate and numerically validate by Monte Carlo simulations an expression for the diffusion coefficient of a two-dimensional lattice gas in a field of immobilized traps. As expected, trapping and crowding both suppress transport but, surprisingly, the diffusion coefficient is non-monotonous. Namely, increasing gas densities increases trap occupancy while crowding is not overpowering, such that the diffusion reaches a maximum. These results should be relevant to interfacial growth phenomena, as discussed in the context of nascent adhesions in cells.
CRIS-Team Scopus Importer:2022-03-25

Cryogenic optical localization provides 3D protein structure data with Angstrom resolution - Weisenburger, Siegfried; Boening, Daniel; Schomburg, Benjamin; Giller, Karin; Becker, Stefan; Griesinger, Christian; Sandoghdar, Vahid (Nature methods, 2017)
We introduce Cryogenic Optical Localization in 3D (COLD), a method to localize multiple fluorescent sites within a single small protein with Angstrom resolution. We demonstrate COLD by determining the conformational state of the cytosolic Per-ARNT-Sim domain from the histidine kinase CitA of Geobacillus thermodenitrificans and resolving the four biotin sites of streptavidin. COLD provides quantitative 3D information about small- to medium-sized biomolecules on the Angstrom scale and complements other techniques in structural biology.
EAM Import::2019-03-13

Dark-Bright Soliton Bound States in a Microresonator - Zhang, Shuangyou; Bi, Toby; Ghalanos, George N.; Moroney, Niall P.; Del Bino, Leonardo; Del'Haye, Pascal (Physical Review Letters, 2022)
Dissipative Kerr solitons in microresonators have facilitated the development of fully coherent, chipscale frequency combs. In addition, dark soliton pulses have been observed in microresonators in the normal dispersion regime. Here, we report bound states of mutually trapped dark-bright soliton pairs in a microresonator. The soliton pairs are generated seeding two modes with opposite dispersion but with similar group velocities. One laser operating in the anomalous dispersion regime generates a bright soliton microcomb, while the other laser in the normal dispersion regime creates a dark soliton via Kerr-induced cross-phase modulation with the bright soliton. Numerical simulations agree well with experimental results and reveal a novel mechanism to generate dark soliton pulses. The trapping of dark and bright solitons can lead to light states with the intriguing property of constant output power while spectrally resembling a frequency comb. These results can be of interest for telecommunication systems, frequency comb applications, and ultrafast optics.
CRIS-Team WoS Importer:2022-02-11

Deciphering a hexameric protein complex with Angstrom optical resolution - Mazal, Hisham; Wieser, Franz-Ferdinand; Sandoghdar, Vahid (eLife, 2022)
Cryogenic optical localization in three dimensions (COLD) was recently shown to resolve up to four binding sites on a single protein. However, because COLD relies on intensity fluctuations that result from the blinking behavior of fluorophores, it is limited to cases where individual emitters show different brightness. This significantly lowers the measurement yield. To extend the number of resolved sites as well as the measurement yield, we employ partial labeling and combine it with polarization encoding in order to identify single fluorophores during their stochastic blinking. We then use a particle classification scheme to identify and resolve heterogenous subsets and combine them to reconstruct the three-dimensional arrangement of large molecular complexes. We showcase this method (polarCOLD) by resolving the trimer arrangement of proliferating cell nuclear antigen (PCNA) and six different sites of the hexamer protein Caseinolytic Peptidase B (ClpB) of Thermus thermophilus in its quaternary structure, both with Angstrom resolution. The combination of polarCOLD and single-particle cryogenic electron microscopy (cryoEM) promises to provide crucial insight into intrinsic heterogeneities of biomolecular structures. Furthermore, our approach is fully compatible with fluorescent protein labeling and can, thus, be used in a wide range of studies in cell and membrane biology.
CRIS-Team WoS Importer:2022-06-17

Deep-ultraviolet to mid-infrared supercontinuum generated in solid-core ZBLAN photonic crystal fibre - Jiang, Xin; Joly, Nicolas; Finger, Martin A.; Babic, Fehim; Wong, Gordon K. L.; Travers, John C.; Russell, Philip St. John (Nature Photonics, 2015)
Silica-based photonic crystal fibre has proven highly successful for supercontinuum generation, with smooth and flat spectral power densities. However, fused silica glass suffers from strong material absorption in the mid-infrared (>2,500 nm), as well as ultraviolet-related optical damage (solarization), which limits performance and lifetime in the ultraviolet (<380 nm). Supercontinuum generation in silica photonic crystal fibre is therefore only possible between these limits. A number of alternative glasses have been used to extend the mid-infrared performance, including chalcogenides, fluorides and heavy-metal oxides, but none has extended the ultraviolet performance. Here, we describe the successful fabrication (using the stack-and-draw technique) of a ZBLAN photonic crystal fibre with a high air-filling fraction, a small solid core, nanoscale features and near-perfect structure. We also report its use in the generation of ultrabroadband, long-term stable, supercontinua spanning more than three octaves in the spectral range 200-2,500 nm.

Deep-UV-enhanced supercontinuum generated in a tapered gas-filled photonic crystal fiber - Suresh, Mallika Irene; Hammer, Jonas; Joly, Nicolas; Russell, Philip St. John; Tani, Francesco (Optics Letters, 2021)
We present the use of a linearly down-tapered gas-filled hollow-core photonic crystal fiber in a single stage, pumped with pulses froma compact infrared (IR) laser source, to generate a supercontinuum (SC) carrying significant spectral power in the deep ultraviolet (UV) [200-300 nm]. The generated SC extends from the near IR down to 213 nm with 0.58 mW/nm and down to 220 nm with 0.83 mW/nm in the deepUV.
CRIS-Team Scopus Importer:2021-09-17

Deflectometric measurement of large mirrors - Olesch, Evelyn; Häusler, Gerd; Wörnlein, André; Stinzing, Friedrich; van Eldik, Christopher (Advanced Optical Technologies, 2014)
We discuss the inspection of large-sized, spherical mirror tiles by 'Phase Measuring Deflectometry' (PMD). About 10 000 of such mirror tiles, each satisfying strict requirements regarding the spatial extent of the point-spreadfunction (PSF), are planned to be installed on the Cherenkov Telescope Array (CTA), a future ground-based instrument to observe the sky in very high energy gamma-rays. Owing to their large radii of curvature of up to 60 m, a direct PSF measurement of these mirrors with concentric geometry requires large space. We present a PMD sensor with a footprint of only 5 ?2 ?1.2 m3 that overcomes this limitation. The sensor intrinsically acquires the surface slope; the shape data are calculated by integration. In this way, the PSF can be calculated for real case scenarios, e.g., when the light source is close to infinity and off-axis. The major challenge is the calibration of the PMD sensor, specifically because the PSF data have to be reconstructed from different camera views. The calibration of the setup is described, and measurements presented and compared to results obtained with the direct approach.
Keywords: 3D-metrology; Deflectometry; Interferometry; Optical testing; Telescope

Deformation of Platonic foam cells: Effect on growth rate - Evans, Myfanwy; Zirkelbach, Johannes; Schröder-Turk, Gerd; Kraynik, Andrew M.; Mecke, Klaus (Physical Review E, 2012)
The diffusive growth rate of a polyhedral cell in dry three-dimensional foams depends on details of shape beyond cell topology, in contrast to the situation in two dimensions, where, by von Neumann's law, the growth rate depends only on the number of cell edges. We analyze the dependence of the instantaneous growth rate on the shape of single foam cells surrounded by uniform pressure; this is accomplished by supporting the cell with films connected to a wire frame and inducing cell distortions by deforming the wire frame. We consider three foam cells with a very simple topology; these are the Platonic foam cells, which satisfy Plateau's laws and are based on the trivalent Platonic solids (tetrahedron, cube, and dodecahedron). The Surface Evolver is used to model cell deformations induced through extension, compression, shear, and torsion of the wire frames. The growth rate depends on the deformation mode and frame size and can increase or decrease with increasing cell distortion. The cells have negative growth rates, in general, but dodecahedral cells subjected to torsion in small wire frames can have positive growth rates. The deformation of cubic cells is demonstrated experimentally.

Demonstrating quantum random with single photons - Bronner, Patrick; Strunz, Andreas; Silberhorn, Christine; Meyn, Jan-Peter (European Journal of Physics, 2009)
We present an experiment for education which demonstrates random transmission or reflection of heralded single photons on beam splitters. With our set-up, we can realize different quantum random experiments by appropriate settings of polarization rotators. The concept of entanglement is motivated by correlated randomness. The experiments are suitable for undergraduate education and are available as interactive screen experiments. © 2009 IOP Publishing Ltd.
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.PI.PDP.demons

Demonstration of a state of light with purely transverse angular momentum - Banzer, Peter; Neugebauer, Martin; Aiello, Andrea; Marquardt, Christoph; Lindlein, Norbert; Bauer, Thomas; Leuchs, Gerd (Optics InfoBase Conference Papers, 2013)
We demonstrate and discuss a state of light with purely transverse angular momentum - a photonic wheel - generated by tight focusing of polarization tailored light. We use an experimental nanoprobing technique to measure the corresponding distribution.
CRIS-Team Scopus Importer:2022-06-05

Demonstration of Near-Optimal Discrimination of Optical Coherent States - Leuchs, Gerd; et al. (Physical Review Letters, 2008)
The optimal discrimination of nonorthogonal quantum states with minimum error probability is a fundamental task in quantum measurement theory as well as an important primitive in optical communication. In this work, we propose and experimentally realize a new and simple quantum measurement strategy capable of discriminating two coherent states with smaller error probabilities than can be obtained using the standard measurement devices: the Kennedy receiver and the homodyne receiver. © 2008 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2008.nat.dphy.optik.1optik.demons

Demonstration of the spatial separation of the entangled quantum side-bands of an optical field - Leuchs, Gerd; et al. (Physical Review A, 2005)
UnivIS-Import:2015-03-09:Pub.2005.nat.dphy.optik.1optik.demons

Depolarized guided acoustic wave Brillouin scattering in hollow-core photonic crystal fibers - Zhong, Wenjia; Stiller, Birgit; Elser, Dominique Alexander; Heim, Bettina; Marquardt, Christoph; Leuchs, Gerd (Optics Express, 2015)
By performing quantum-noise-limited optical heterodyne detection, we observe polarization noise in light after propagation through a hollow-core photonic crystal fiber (PCF). We compare the noise spectrum to the one of a standard fiber and find an increase of noise even though the light is mainly transmitted in air in a hollow-core PCF. Combined with our simulation of the acoustic vibrational modes in the hollow-core PCF, we are offering an explanation for the polarization noise with a variation of guided acoustic wave Brillouin scattering (GAWBS). Here, instead of modulating the strain in the fiber core as in a solid core fiber, the acoustic vibrations in hollow-core PCF influence the effective refractive index by modulating the geometry of the photonic crystal structure. This induces polarization noise in the light guided by the photonic crystal structure.
CRIS-Team Scopus Importer:2021-06-29

Design and fabrication of nanowire metal grating polarizers for a shearing interferometer using polarization marking - Ghadyani, Zahra; Harder, Irina; Rusina, Olga; Iff, Wolfgang; Nercissian, Vanusch; Mantel, Klaus Peter; Lindlein, Norbert; Leuchs, Gerd (Proceedings of the EOS Topical Meeting on Diffractive Optics 2010, 2010)

Design and modeling of a miniature system containing micro-optics - Lindlein, Norbert; et al. (Proceedings of SPIE, 2001)
The design and modeling of micro-optical systems is still a challenging task because classical methods like ray tracing do not take into account diffraction effects and other coherent effects which appear e.g. in the presence of micro-optical array systems. On the other side, there exist scalar or rigorous diffraction theories to model optical systems. But they are also limited in their applications because they either neglect non-paraxial effects or the calculation time is too high for a practical use. In this paper we will therefore give an overview about existing (scalar) theories to model optical systems, especially systems containing micro-optics: a simple paraxial matrix theory, ray tracing, Gaussian beam propagation and the propagation of a wave using the angular spectrum of plane waves. The advantages and disadvantages of these theories will be shown and compared. At the end we will describe a combination of ray tracing and wave propagation methods to give a more realistic simulation of micro-optical systems.
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.optik.1optik.design
Keywords: Angular spectrum of plane waves; Diffraction theories; Gaussian beams; Micro-optics; Modeling of optical systems; Optical design; Ray tracing

Design and simulation rules for printed optical waveguides with implemented scattering methods in CAD and raytracing software - Loosen, Florian; Backhaus, Carsten; Lindlein, Norbert; Zeitler, Jochen Tobias; Franke, Jörg (Proceeding, 117. DGaO-Jahrestagung, 2016)
The printing process of polymer optical waveguides is a new and uncharted research topic, which the research group OPTAVER is principally involved in. A main consequence of the printing process is the roughness of the interface between core and cladding. This surface between the dielectric media creates scattering in printed waveguides. To simulate this behaviour, standard non-sequential raytracing methods have to be extended with scattering algorithms. Here, scattering power spectra for each incident ray interacting with the rough surface are generated using the perturbation theory. Another task is to connect MID-speciﬁc CAD tools with raytracing simulations to create a holistic tool for design and validation of light propagation. This tool is specifically prepared to analyze the manufacturing process of polymer optical waveguides. This technique facilitates new applications in different research and development fields. Comparing the performances of real printed and simulated polymer optical waveguides is one of the major links between the different researchers of this DFG research group.
Keywords: Optisches Design; Optische Systeme; Optische Informationsübertragung

Design considerations for the absolute testing approach of aspherics using combined diffractive optical elements - Lindlein, Norbert; Schwider, Johannes; Harder, Irina; Mantel, Klaus Peter; Khan, Gufran S. (Applied Optics, 2007)
Aspheric optical surfaces are often tested using diffractive optics as null elements. For precise measurements, the errors caused by the diffractive optical element must be calibrated. Recently, we reported first experimental results of a three position quasi-absolute test for rotationally invariant aspherics by using combined-diffractive optical elements (combo-DOEs). Here we investigate the effects of the DOE substrate errors on the proposed calibration procedure and present a set of criteria for designing an optimized combo-DOE. It is demonstrated that this optimized design enhances the overall consistency of the procedure. Furthermore, the rotationally varying part of the surface deviations is compared with the rotationally varying deviations obtained by an N-position averaging procedure and is found to be in good agreement. © 2007 Optical Society of America.
UnivIS-Import:2015-04-14:Pub.2007.nat.dphy.optik.1optik.design_9

Design criteria for combined diffractive optical elements for quasi-absolute testing of aspherics - Lindlein, Norbert; et al. (Frontiers in Optics, FiO 2007, 2007)
Recently, we reported first experimental results of a three position quasi-absolute test for rotationally symmetric aspherics by using combined diffractive optical elements (Combo-DOEs). Here we investigate several systematic error sources and present an optimised Combo-DOE. © 2007 Optical Society of America.

Design of a mode converter for efficient light-atom coupling in free space - Sondermann, Markus; Maiwald, Robert; Konermann, Hildegard; Lindlein, Norbert; Peschel, Ulf; Leuchs, Gerd (Applied Physics B-Lasers and Optics, 2007)
In this article, we describe how to develop a mode converter that transforms a plane electromagnetic wave into an inward-moving dipole wave. The latter one is intended to bring a single atom or ion from its ground state to an excited state by absorption of a single photon wave packet with near-100% efficiency. © 2007 Springer-Verlag.
UnivIS-Import:2015-03-09:Pub.2007.nat.dphy.optik.1optik.design

Design und Herstellung eines CGH-basierten Modalen Wellenfrontsensors - Stehr, Johannes; Loosen, Florian; Lindlein, Norbert; Alber, Lucas (118. DGaO-Jahrestagung, 2017)
Modale Wellenfrontsensoren können gegenüber einer zonalen Wellenfrontdetektion von Vorteil sein. Etwa, wenn in einem optischen Element fabrikationsbedingt nur spezielle Aberrationsmoden zu erwarten sind. Der Hauptvorteil eines modalen Sensors ist die geringe Auswertekomplexität und folglich ein Geschwindigkeitsvorteil bei der Wellenfrontmessung. Als modale Basis können die Zernike-Polynome dienen, deren Koeffizienten durch Messung der Phasenfront bestimmt werden können. Sind die zu erwartenden Aberrationen für ein optisches Element bekannt, kann die Funktionsweise diesbezüglich optimiert werden. Unser Ziel ist es, einen Wellenfrontsensor auf Basis eines Computer-Generierten Hologramms zu realisieren (Neil et al. 2000). Das Prinzip des Sensors basiert auf der holografischen Rekonstruktion einer ebenen Objektwelle durch eine spezifisch aberrierte Referenzwellenfront. Wir werden die quantitative Untersuchung des intermodalen Crosstalks eines modalen Wellenfrontsensors präsentieren, welcher zur genauen Messung von Defokus und Koma ausgelegt ist. Die Charakterisierung des intermodalen Crosstalks ist dabei notwendig, um ein möglichst effizientes und genaues Sensorverhalten zu erzielen.

Detecting the spatial quantum uncertainty of bosonic systems - Chille, Vanessa; Treps, Nicolas; Fabre, Claude; Leuchs, Gerd; Marquardt, Christoph; Aiello, Andrea (New Journal of Physics, 2016)
We present the quantum theory of direct detection of bosonic particles by multipixel detectors. For the sake of clarity, we specialize on beams of photons, and we study the measurement of different spatial beam characteristics, as position and width. The limits of these measurements are set by the quantum nature of the light field. We investigate how both, detector imperfections and finite pixel size affect the photon counting distribution. An analytic theory for the discretized detection setup is derived. We discuss the results and compare them to the theory presented by Chille et al 2015 Opt. Express 23 32777, which investigates the beam width noise independently of the measurement system. Finally, we present numerical simulations that furnish realistic and promising predictions for possible experimental studies.
CRIS-Team Scopus Importer:2022-06-05
Keywords: bosonic systems; quantum uncertainty; spatial measurements

Detection-device-independent verification of nonclassical light - Bohmann, Martin; Qi, Luo; Vogel, Werner; Chekhova, Maria (Physical Review Research, 2019)
The efficient certification of nonclassical effects of light forms the basis for applications in optical quantum technologies. We derive general correlation conditions for the verification of nonclassical light based on multiplexed detection. The obtained nonclassicality criteria are valid for imperfectly balanced multiplexing scenarios with on-off detectors and do not require any knowledge about the detector system. In this sense, they are fully independent of the detector system. In our experiment, we study light emitted by clusters of single-photon emitters, whose photon number may exceed the number of detection channels. Even under such conditions, our criteria certify nonclassicality with high statistical significance.
CRIS-Team WoS Importer:2021-10-18

Device Calibration Impacts Security of Quantum Key Distribution - Jain, Nitin; Wittmann, Christoffer; Lydersen, Lars; Wiechers, Carlos; Elser, Dominique Alexander; Marquardt, Christoph; Makarov, Vadim; Leuchs, Gerd (Physical Review Letters, 2011)
Characterizing the physical channel and calibrating the cryptosystem hardware are prerequisites for establishing a quantum channel for quantum key distribution (QKD). Moreover, an inappropriately implemented calibration routine can open a fatal security loophole. We propose and experimentally demonstrate a method to induce a large temporal detector efficiency mismatch in a commercial QKD system by deceiving a channel length calibration routine. We then devise an optimal and realistic strategy using faked states to break the security of the cryptosystem. A fix for this loophole is also suggested. © 2011 American Physical Society.
CRIS-Team Scopus Importer:2022-06-05

Dicke superradiance and hanbury brown and twiss intensity interference: Two sides of the same coin - Wiegner, Ralph; Oppel, Steffen; Bhatti, Daniel; Agarwal, Girish S.; von Zanthier, Joachim (Optics InfoBase Conference Papers, 2017)
We show that Hanbury Brown and Twiss intensity interference and Dicke superradiance can be considered as two sides of the same coin, resulting from multi-photon interferences appearing in higher order photon correlations.
CRIS-Team Scopus Importer:2023-03-27

Die Optik - eine physikalische Disziplin im Aufwind bietet Chancen für Deutschland - Leuchs, Gerd; et al. (LaserOpto, 1999)
UnivIS-Import:2015-03-05:Pub.1999.nat.dphy.optik.1optik.dieopt

Differential Diffusional Properties in Loose and Tight Docking Prior to Membrane Fusion - Witkowska, Agata; Spindler, Susann; Mahmoodabadi, Reza Gholami; Sandoghdar, Vahid; Jahn, Reinhard (Biophysical Journal, 2020)
Fusion of biological membranes, although mediated by divergent proteins, is believed to follow a common pathway. It proceeds through distinct steps, including docking, merger of proximal leaflets (stalk formation), and formation of a fusion pore. However, the structure of these intermediates is difficult to study because of their short lifetime. Previously, we observed a loosely and tightly docked state preceding leaflet merger using arresting point mutations in SNARE proteins, but the nature of these states remained elusive. Here, we used interferometric scattering (iSCAT) microscopy to monitor diffusion of single vesicles across the surface of giant unilamellar vesicles (GUVs). We observed that the diffusion coefficients of arrested vesicles decreased during progression through the intermediate states. Modeling allowed for predicting the number of tethering SNARE complexes upon loose docking and the size of the interacting membrane patches upon tight docking. These results shed new light on the nature of membrane-membrane interactions immediately before fusion.
CRIS-Team Scopus Importer:2020-12-11

Differential ray tracing for an improved simulation of incoherent illumination systems - Lindlein, Norbert; et al. (Frontiers in Optics, FiO 2008, 2008)
Analyzing intensity distributions is of great importance for today's illumination systems design. Contrary to Monte-Carlo techniques, differential ray tracing possesses great potential to improve simulation efficiency by reducing computational time while concurrently showing accurate results. © 2008 Optical Society of America.

Different types of coherence: Young-type interference versus Dicke superradiance - Bhatti, Daniel; Bojer, Manuel; von Zanthier, Joachim (Physical Review A, 2021)
Dicke superradiance, i.e., the enhanced spontaneous emission of coherent radiation, is often attributed to radiation emitted by synchronized dipoles coherently oscillating in phase. At the same time, Dicke derived superradiance assuming atoms in entangled Dicke states which do not display any dipole moment. To shed light on this apparent paradox, we study the intensity distribution arising from two identical two-level atoms prepared either in an entangled Dicke state or in a separable atomic state with a nonvanishing dipole moment. We find that the two configurations produce similar far-field intensity patterns, although they stem from fundamentally distinct types of coherence: while in the second case the atoms display coherence among the individual particles, leading to Young-type interference like that known from classical dipoles, atoms in Dicke states possess collective quantum coherence stemming from entanglement and quantum correlations of the state, leading to an interference pattern resulting from enhanced spontaneous emission. This demonstrates that the radiation generated by synchronized dipoles and Dicke superradiance - even if they do produce the same interference pattern - are fundamentally distinct phenomena and have to be interpreted in different ways.
CRIS-Team Scopus Importer:2021-11-26

Diffraction limited holographic lenses in dichromated gelatine - Lindlein, Norbert; et al. (Optical Engineering, 1996)
Holographic lenses in volume media suffer from the mismatch between the recording and the reconstruction wavelength. The lenses are recorded in the blue spectral range because of spectral sensitivity of the recording material. The lenses investigated here are reconstructed with red light. The aim of this work is the realization of diffraction-limited holographic lenses with a high diffraction efficiency in the presence of a wavelength mismatch. Therefore the lenses have to be recorded with at least one aspheric recording wavefront in order to fulfill the Bragg condition on the one hand and to correct the wave aberrations on the other. We propose an iterative optimization procedure which also eliminates the wave aberrations caused by the misalignments of the recording setup. This optimization procedure requires the accurate measurement of the wave aberrations. These aberrations are eliminated by an appropriate modification of the aspheric recording wavefront. In this paper the design principle, the recording setup, the interferometric measurement, and the iterative optimization procedure are given. This optimization procedure results in diffraction-limited holographic lenses. © 1996 Society of Photo-Optical Instrumentation Engineers.
UnivIS-Import:2015-03-05:Pub.1996.nat.dphy.optik.1optik.diffra
Keywords: Dichromated gelatine; Holographic lenses; Holographic optical elements; Thick phase gratings; Wave aberration; Wavelength mismatch

Diffractive complete lateral shearing interferometer with reduced coherence - Harder, Irina; Nercissian, Vanusch; Schwider, Johannes; Berger, Andreas; Mantel, Klaus Peter; Lindlein, Norbert (Proceedings of the EOS Topical Meeting on Diffractive Optics 2010, 2010)

Diffractive lateral shearing interferometer for phase shift mask measurement using an excimer laser source - Lindlein, Norbert; et al. (Eighth International Symposium on Laser Metrology, 2005)
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 in series 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. The state of the art of our experiments will be presented.

Diffractive simultaneous bidirectional shearing interferometry using tailored spatially coherent light - Nercissian, Vanusch; Harder, Irina; Mantel, Klaus Peter; Berger, Andreas; Leuchs, Gerd; Lindlein, Norbert; Schwider, Johannes (Applied Optics, 2011)

Diffractive simultaneous lateral shearing interferometry - Lindlein, Norbert; et al. (Optical Measurement Systems for Industrial Inspection VII, 2011)
A lateral shearing interferometer usually provides the slope data of a wave front under test along one direction. For the complete reconstruction of the wavefront, two slope datasets along different directions are required. Based on diffractive gratings, a simultaneous measurement of bothdata sets can be carried out. Two possible realizations are presented using a polarization signature and a partially coherent light source. © 2011 SPIE.
Keywords: Diffraction gratings; Interferometry; Spatial coherence

Diffractive Systems: Aberration Correction with Diffractive Elements - Lindlein, Norbert (Encyclopedia of Modern Optics, 2004)
UnivIS-Import:2015-04-20:Pub.2004.nat.dphy.optik.1optik.diffra

Diffraktive optische Elemente zur Lichtmanipulation - Schwider, Johannes; Dresel, Thomas; Beyerlein, Mathias; Harder, Irina; Lindlein, Norbert; Collischon, Martin; Leuchs, Gerd (2001)
UnivIS-Import:2015-04-14:Pub.2001.nat.dphy.optik.1optik.diffra

Diffraktives 2D-Shearing-Interferometer mit partieller rÃa4umlicher KohÃa4renz - Nercissian, Vanusch; Mantel, Klaus; Harder, Irina; Berger, Andreas; Schwider, Johannes; Lindlein, Norbert (DGaO-Proceedings, 2010)

Digitizing 3D objects for Reverse Engineering and Virtual Reality - Häusler, Gerd; et al. (Principles of 3D Image Analysis andSynthesis, 2000)
UnivIS-Import:2015-04-20:Pub.2000.nat.dphy.optik.1optik.digiti

Direct experimental test of non-separability and other quantum techniques using continuous variables of light - Korolkova, Natalia; Silberhorn, Christine; Glöckl, Oliver; Lorenz, Stefan; Marquardt, Christoph; Leuchs, Gerd (European Physical Journal D, 2002)
We present schemes for the generation and evaluation of continuous variable entanglement of bright optical beams and give a brief overview of a variety of optical techniques and quantum communication applications on this basis. A new entanglement-based quantum interferometry scheme with bright beams is suggested. The performance of the presented schemes is independent of the relative interference phase which is advantageous for quantum communication applications. © EDP Sciences, Springer-Verlag, Società Italiana di Fisica 2002.
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.direct

Direct integration of the S-matrix applied to rigorous diffraction - Iff, Wolfgang; Lindlein, Norbert; Tishchenko, A. V. (Journal of Optics, 2014)

Directional Dicke Subradiance with Nonclassical and Classical Light Sources - Bhatti, Daniel; Schneider, Raimund; Oppel, Steffen; von Zanthier, Joachim (Physical Review Letters, 2018)
We investigate Dicke subradiance of N >= 2 distant quantum sources in free space, i.e., the spatial emission patterns of spontaneously radiating noninteracting multilevel atoms or multiphoton sources, prepared in totally antisymmetric states. We find that the radiated intensity is marked by a full suppression of spontaneous emission in particular directions. In resemblance to the analogous, yet inverted, superradiant emission profiles of N distant two-level atoms prepared in symmetric Dicke states, we call the corresponding emission patterns directional Dicke subradiance. We further derive that higher-order intensity correlations of the light emitted by statistically independent thermal light sources display the same directional Dicke subradiant behavior and show that it stems from the same interference phenomenon as in the case of quantum sources. We finally present measurements of directional Dicke subradiance for N = 2,...,5 distant thermal light sources corroborating the theoretical finding

Directional Superradiant Emission from Statistically Independent Incoherent Nonclassical and Classical Sources - Oppel, Steffen; Wiegner, Ralph; Agarwal, Girish Saran; von Zanthier, Joachim (Physical Review Letters, 2014)
Superradiance has been an outstanding problem in quantum optics since Dicke introduced the concept of enhanced directional spontaneous emission by an ensemble of identical two-level atoms. The effect is based on the correlated collective Dicke states which turn out to be highly entangled. Here we show that enhanced directional emission of spontaneous radiation can be produced also with statistically independent incoherent sources, via the measurement of higher-order correlation functions of the emitted radiation. Our analysis is applicable to a wide variety of quantum emitters, like trapped atoms, ions, quantum dots, or nitrogen-vacancy centers, and is also valid for incoherent classical emitters. This is experimentally confirmed with up to eight statistically independent thermal light sources. The arrangement to measure the higher-order correlation functions corresponds to a generalized Hanbury Brown-Twiss setup, demonstrating that the two phenomena, superradiance and the Hanbury Brown-Twiss effect, stem from the same interference phenomeno

Direct measurement of the coupled spatiotemporal coherence of parametric down-conversion under negative group-velocity dispersion - Cutipa Giménez, Paula; Spasibko, Kirill Yu; Chekhova, Maria (Optics Letters, 2020)
We present a direct measurement of the spatiotemporal coherence of parametric down-conversion in the range of negative group-velocity dispersion. In this case, the frequency-angular spectra are ring-shaped, and temporal coherence is coupled to spatial coherence. Correspondingly, the lack of coherence due to spatial displacement can be compensated for with the introduction of time delay. We show a simple technique, based on a modified Mach-Zehnder interferometer, which allows us to measure time coherence and near-field space coherence simultaneously, with complete control over both variables. This technique is also suitable for the measurement of second-order coherence, where the main applications are related to two-photon spectroscopy.
CRIS-Team Scopus Importer:2020-07-24

Direct measurement of the geometric spin hall effect of light - Korger, Jan; Aiello, Andrea; Chille, Vanessa; Wittmann, Christoffer; Banzer, Peter; Lindlein, Norbert; Marquardt, Christoph; Leuchs, Gerd (Frontiers in Optics, FIO 2012, 2012)
We experimentally demonstrate a recently predicted novel beam shift phenomenon, the geometric spin Hall effect of light. This effect is fundamentally different from ordinary beam shifts due to its purely geometric nature. © OSA 201

Discontinuous space variant sub-wavelength structures for generating radially polarized light in visible region - Ghadyani, Zahra; Rothau, Sergej; Lindlein, Norbert; Leuchs, Gerd; Lohse, Olga; Harder, Irina (Journal of the European Optical Society: Rapid Publications, 2011)

Discover better optical sensors - By exploring and exploiting nature's limits - Häusler, Gerd (Optics InfoBase Conference Papers, 2019)
Nature's limits are precious: they often reveal uncertainty products connecting coherence, resolution, precision, channel capacity… So we can bargain with nature for "optimal" 3D sensors with novel features or just better precision, resolution, speed.
CRIS-Team Scopus Importer:2021-04-20

Discrimination of optical coherent states using a photon number resolving detector - Wittmann, Christoffer; Andersen, Ulrik Lund; Leuchs, Gerd (Journal of Modern Optics, 2010)
The discrimination of non-orthogonal quantum states with reduced or without errors is a fundamental task in quantum measurement theory. In this work, we investigate a quantum measurement strategy capable of discriminating two coherent states probabilistically with significantly smaller error probabilities than can be obtained using non-probabilistic state discrimination. We find that appropriate postselection of the measurement data of a photon number resolving detector can be used to discriminate two coherent states with small error probability. We compare our new receiver to an optimal intermediate measurement between minimum error discrimination and unambiguous state discrimination.
UnivIS-Import:2015-03-09:Pub.2010.nat.dphy.optik.1optik.discri
Keywords: Quantum information; Quantum receivers; Quantum state discrimination

Disentangling the effects of nanoscale structural variations on the light emission wavelength of single nano-emitters: InGaN/GaN multiquantum well nano-LEDs for a case study - Sarau, George; Heilmann, Martin; Latzel, Michael; Christiansen, Silke (Nanoscale, 2014)
The scattering in the light emission wavelength of semiconductor nano-emitters assigned to nanoscale variations in strain, thickness, and composition is critical in current and novel nanotechnologies from highly efficient light sources to photovoltaics. Here, we present a correlated experimental and theoretical study of single nanorod light emitting diodes (nano-LEDs) based on InGaN/GaN multiquantum wells to separate the contributions of these intrinsic fluctuations. Cathodoluminescence measurements show that nano-LEDs with identical strain states probed by non-resonant micro-Raman spectroscopy can radiate light at different wavelengths. The deviations in the measured optical transitions agree very well with band profile calculations for quantum well thicknesses of 2.07-2.72 nm and In fractions of 17.5-19.5% tightly enclosing the growth values. The nanorod surface roughness controls the appearance of surface optical phonon modes with direct implications on the design of phonon assisted nano-LED devices. This work establishes a new, simple, and powerful methodology for fundamental understanding as well as quantitative analysis of the strain - light emission relationship and surface-related phenomena in the emerging field of nano-emitters.
EAM Import::2019-03-13

Dispersion engineering of Schott-SF6 photonic crystal fibres for nonlinear applications in the infrared - Joly, Nicolas; Jiang, X.; Pennetta, Riccardo; Hammer, Jonas; Babic, F.; Russell, Philip St. John (Optics InfoBase Conference Papers, 2019)
An empirical model for estimating the dispersion of solid-core Schott-SF6 photonic crystal fibre is presented. Finite element calculations and experimentally measured power-dependent spectra confirm the accuracy of the model.
CRIS-Team Scopus Importer:2019-07-09

Distillation of Squeezing from Non-Gaussian Quantum States - Heersink, Joel; Marquardt, Christoph; Dong, Ruifang; Filip, Radim; Lorenz, Stefan; Leuchs, Gerd; Andersen, Ulrik Lund (Physical Review Letters, 2006)
We show that single copy distillation of squeezing from continuous variable non-Gaussian states is possible using linear optics and conditional homodyne detection. A specific non-Gaussian noise source, corresponding to a random linear displacement, is investigated experimentally. Conditioning the signal on a tap measurement, we observe probabilistic recovery of squeezing. © 2006 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2006.nat.dphy.optik.1optik.distil

Distillation of squeezing using an engineered pulsed parametric down-conversion source - Dirmeier, Thomas; Tiedau, Johannes; Khan, Imran; Ansari, Vahid; Müller, Christian; Silberhorn, Christine; Marquardt, Christoph; Leuchs, Gerd (Optics Express, 2020)
Hybrid quantum information processing combines the advantages of discrete and continues variable protocols by realizing protocols consisting of photon counting and homodyne measurements. However, the mode structure of pulsed sources and the properties of the detection schemes often require the use of optical filters in order to combine both detection methods in a common experiment. This limits the efficiency and the overall achievable squeezing of the experiment. In our work, we use photon subtraction to implement the distillation of pulsed squeezed states originating from a genuinely spatially and temporally single-mode parametric down-conversion source in non-linear waveguides. Due to the distillation, we witness an improvement of 0.17 dB from an initial squeezing value of -1.648 +/- 0.002 dB, while achieving a purity of 0.58, and confirm the non-Gaussianity of the distilled state via the higher-order cumulants. With this, we demonstrate the source's suitability for scalable hybrid quantum network applications with pulsed quantum light. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
CRIS-Team WoS Importer:2020-11-13

Distributing entanglement with separable states - Peuntinger, Christian; Chille, Vanessa; Mista, Ladislav; Korolkova, Natalia; Foertsch, Michael; Korger, Jan; Marquardt, Christoph; Marquardt, Christoph; Leuchs, Gerd (Physical Review Letters, 2013)
We experimentally demonstrate a protocol for entanglement distribution by a separable quantum system. In our experiment, two spatially separated modes of an electromagnetic field get entangled by local operations, classical communication, and transmission of a correlated but separable mode between them. This highlights the utility of quantum correlations beyond entanglement for the establishment of a fundamental quantum information resource and verifies that its distribution by a dual classical and separable quantum communication is possible. © 2013 American Physical Society.
CRIS-Team Scopus Importer:2022-06-05

Distribution of squeezed states through an atmospheric channel - Peuntinger, Christian; Heim, Bettina; Mueller, Christian R.; Gabriel, Christian; Marquardt, Christoph; Leuchs, Gerd (Physical Review Letters, 2014)
Continuous variable quantum states of light are used in quantum information protocols and quantum metrology and known to degrade with loss and added noise. We were able to show the distribution of bright polarization squeezed quantum states of light through an urban free-space channel of 1.6 km length. To measure the squeezed states in this extreme environment, we utilize polarization encoding and a postselection protocol that is taking into account classical side information stemming from the distribution of transmission values. The successful distribution of continuous variable squeezed states is accentuated by a quantum state tomography, allowing for determining the purity of the state. © 2014 American Physical Society.
CRIS-Team Scopus Importer:2022-06-05

Diversity Detection of Speckles for Double-Wavelength Interferometry on Rough Surfaces - Leuchs, Gerd; et al. (Applied Optics, 2002)
When the topography of a rough surface is measured with a double-wavelength interferometer, the phase error of the signal corresponding to the synthetic wavelength increases in the vicinity of dark speckles. To overcome this problem we perform an amplitude-dependent averaging of the synthetic phase over independent speckles (diversity detection). We either use spatially neighboring speckles or in the case of depolarizing surfaces, we use speckles of the same spatial mode, but with orthogonal polarizations. For the latter case the lateral resolution stays unaffected. The reduction of the speckle noise is demonstrated experimentally for a laterally scanning double-wavelength interferometer with superheterodyne detection of the synthetic phase. © 2002 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.divers

Doppler velocimetry on microparticles trapped and propelled by laser light in liquid-filled photonic crystal fiber - Garbos, M. K.; Euser, T. G.; Schmidt, O. A.; Unterkofler, S.; Russell, Philip St. John (Optics Letters, 2011)
Laser Doppler velocimetry is used to measure very accurately the velocity and position of a microparticle propelled and guided by laser light in liquid-filled photonic crystal fiber. Periodic variations in particle velocity are observed that correlate closely with modal beating between the two lowest order guided fiber modes.
EAM Import::2019-03-13

DPSK Signal Regeneration Using a Nonlinear Amplifying Loop Mirror - Sponsel, Klaus; Stephan, Christian; Cvecek, Kristian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Conf. Proc. OFC, Paper OThB2, March, 2007)
Power characteristics and phase functions of a NALM are investigated in simulations and experimentally, showing a phase-preserving nonlinear characteristics suitable for amplitude regeneration of phase-encoded signals. A negative power penalty of -1.5 dB was obtained. ©2006 Optical Society of America.
UnivIS-Import:2017-12-18:Pub.2007.tech.IE.LEH.dpsksi

Drei-Stellungstest für Asphären: Steigerung der Genauigkeit - Geist, Eduard; Mantel, Klaus Peter; Harder, Irina; Lindlein, Norbert (DGAO-Proceedings, 2010)
Keywords: Jahrestagung der DGaO

Dual-colour-pump broadband CARS in single-ring gas-filled photonic crystal fibre - Tyumenev, R.; Spath, L.; Trabold, B. M.; Ahmed, G.; Frosz, M. H.; Russell, Philip St. John (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Selective detection and chemical analysis of trace gases at concentration levels of parts per million (ppm) and below is of critical importance in environmental monitoring [1] and medicine [2]. Spectroscopic techniques offer high gas-type selectivity and are widely used for measuring the concentration of specific molecular species. Raman spectroscopy provides two key advantages. First, the pump wavelength can be freely chosen, independently of the absorption lines of the gas. Second, the highest Raman frequency shift of any gas is the vibrational transition of H2 at 125 THz, which means that all known Raman active molecules can be detected with one spectrometer [3].
CRIS-Team Scopus Importer:2019-11-15

Dual-wave-front computer-generated holograms for quasi-absolute testing of aspherics. - Beyerlein, Mathias; Lindlein, Norbert; Schwider, Johannes (Applied Optics, 2002)
Testing of aspherics by means of computer-generated holograms (CGHs) is well known. To perform a quasi-absolute test of rotationally symmetric aspheric surfaces, two wave fronts must be encoded in the CGH. Both the null lens and a spherical lens have to be stored. This enables successive measurements of the aspheric and of a cat's-eye position without changing the object arm of the interferometer. Two possibilities for encoding both wave fronts have been investigated. A first-order approximation for estimating the influence of disturbing diffraction orders is given.
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.dualwa

Dynamically reconfigurable fibre optical spanner - Kolb, Thorsten; Albert, Sahradha; Haug, Michael; Whyte, Graeme (Lab on A Chip, 2014)
In this paper we describe a pneumatically actuated fibre-optic spanner integrated into a microfluidic Lab-on-a-Chip device for the controlled trapping and rotation of living cells. The dynamic nature of the system allows interactive control over the rotation speed with the same optical power. The use of a multi-layer device makes it possible to rotate a cell both in the imaging plane and also in a perpendicular plane allowing tomographic imaging of the trapped living cell. The integrated device allows easy operation and by combining it with high-resolution confocal microscopy we show for the first time that the pattern of rotation can give information regarding the sub-cellular composition of a rotated cell.
EAM Import::2019-03-13

Dynamic array spot shaping for laser micro machining - Lindlein, Norbert; et al. (Laser Beam Shaping X, 2009)
Laser manufacturing of microstructures using a single focus is a well known technology. Multi-spot optics are applied for process parallelizing if the demand on throughput in mass production rises or large areas of material have to be processed. Diffractive optical elements (DOEs) are used for parallel laser processing of a repetitive structure. These elements split the beam into a periodic spot pattern, where each spot shows the same shape and energy. This allows simultaneous manufacturing of several equal shaped structures at the same time. For patterning a surface this is state of the art and the appropriate technique to reduce processing time while maintaining a high lateral resolution as well as a good relative positioning of the structure due to the DOE. We investigate the usage of microlens arrays as multifunctional elements for forming an arbitrary shaped laser beam into a spot-, a ring-spot- or a line-array pattern. It can be shown that the intensity distribution of each spot is equal to the intensity distribution of all other spots in the whole pattern. The shape of the spots is defined by the angular distribution of the incident beam. We demonstrate that besides other optical properties the output beam profile strongly depends on the Fresnel-Number and is influenced by diffraction and interference effects. We present important design rules which consider geometrical and physical optics. The properties of the spot arrays, like spot diameter, Rayleigh length and beam divergence in dependency of beam and system properties are investigated. Finally we will show some laser micro structuring and micro drilling results in different materials. © 2009 SPIE.
Keywords: Flys Eye Condenser; Laser Beam Homogenizer; Material Processing; Micro Optics; Spot Array Generator

Dynamic Brillouin cooling for continuous optomechanical systems - Zhu, Chang Long; Stiller, Birgit (Materials for Quantum Technology, 2023)
Up until now, ground state cooling using optomechanical interaction is realized in the regime where optical dissipation is higher than mechanical dissipation. Here, we demonstrate that optomechanical ground state cooling in a continuous optomechanical system is possible by using backward Brillouin scattering while mechanical dissipation exceeds optical dissipation which is the common case in optical waveguides. The cooling is achieved in an anti-Stokes backward Brillouin process by modulating the intensity of the optomechanical coupling via a pulsed pump to suppress heating processes in the strong coupling regime. With such dynamic modulation, a significant cooling factor can be achieved, which can be several orders of magnitude lower than for the steady-state case. This modulation scheme can also be applied to Brillouin cooling generated by forward intermodal Brillouin scattering.
CRIS-Team Scopus Importer:2023-05-05
Keywords: Brillouin scattering; mechanical cooling; optomechanics; quantum optics

Dynamic control of higher-order modes in hollow-core photonic crystal fibers - Euser, Tijmen; Whyte, Graeme; Scharrer, Michael; Chen, J. S. Y.; Abdolvand, Amir; Nold, J.; Kaminski, C. F.; Russell, Philip St. John (Optics Express, 2008)
We present a versatile method for selective mode coupling into higher-order modes of photonic crystal fibers, using holograms electronically generated by a spatial light modulator. The method enables non-mechanical and completely repeatable changes in the coupling conditions. We have excited higher order modes up to LP31 in hollow-core photonic crystal fibers. The reproducibility of the coupling allows direct comparison of the losses of different guided modes in both hollow-core bandgap and kagome-lattice photonic crystal fibers. Our results are also relevant to applications in which the intensity distribution of the light inside the fiber is important, such as particle- or atom-guidance.
EAM Import::2019-03-13

Dynamic range expansion of a Shack-Hartmann sensor by use of a modified unwrapping algorithm - Lindlein, Norbert; et al. (Optics Letters, 1998)
An algorithm for expanding the dynamic range of Shack-Hartmann sensors is proposed. The distribution of the spot dislocations is treated with a modified unwrapping algorithm that is widely used in interferometry. The algorithm unwraps the spot dislocations and assigns the spots to their original subapertures, leading to a huge expansion of the dynamic range. For the proposed algorithm there remains a limitation on the maximum wave-front curvature instead of on the maximum wave-front slope. Examples are given that show spot fields that were wrapped four times; the measured wave front had a peak-to-valley value of 116λ. © 1998 Optical Society of America.
UnivIS-Import:2015-03-05:Pub.1998.nat.dphy.optik.1optik.dynami

Dynamics of Development of Laser-Induced Structures on the Surface of a Titanium Alloy - Fomicheva, Iana; Druzhinin, Petr; Amler, Hans; Schuesslbauer, Wolfgang; Christiansen, Silke; Leuchs, Gerd (Proceedings of SPIE - The International Society for Optical Engineering, 2023)
We investigated the dynamics of LSFL (Low Spatial Frequency LIPSS) evolution on the titanium alloy surface. To create them, 12 W picosecond 1.064 μm laser with a pulse repetition rate from 50 kHz to 500 kHz was used. For different laser repetition rate (500, 150, 100 and 50 kHz), the ranges of LSFL periods and peak Fluence of pulse (Fp) for which the maximum period is reached were determined. We also determined the laser parameters at which the resulting LSFL have good quality and uniformity, regardless of the initial surface roughness.
CRIS-Team Scopus Importer:2023-06-02
Keywords: HSFL; LIPSS; LSFL; surface patterning; Ti6Al4V; titanium alloy

Eavesdropper localization for quantum and classical channels via nonlinear scattering - Popp, Alexandra; Sedlmeir, Florian; Stiller, Birgit; Marquardt, Christoph (Optica Quantum, 2024)
Optical fiber networks are part of the important critical infrastructure and known to be prone to eavesdropping attacks. Hence, cryptographic methods have to be used to protect communication. Quantum key distribution (QKD), at its core, offers information theoretical security based on the laws of physics. In deployments, one has to take into account practical security and resilience. The latter includes the localization of a possible eavesdropper after an anomaly has been detected by the QKD system to avoid denial-of-service. Here, we present an approach to eavesdropper location that can be employed in quantum as well as classical channels using stimulated Brillouin scattering. The tight localization of the acoustic wave inside the fiber channel using correlated pump and probe waves allows discovery of the coordinates of a potential threat within centimeters. We demonstrate that our approach outperforms conventional optical time-domain reflectometry (OTDR) in the task of localizing an evanescent outcoupling of 1% with centimeter precision inside standard optical fibers. The system is furthermore able to clearly distinguish commercially available standard SMF28 from different manufacturers, paving the way for fingerprinted fibers in high-security environments.<br

Editorial: Future directions in novel laser source development: Dynamical properties, and beam manipulation - Fu, Xing; Euser, Tijmen; Huang, Shu Wei; Joly, Nicolas; Xie, Shangran (Frontiers in Physics, 2022)
CRIS-Team Scopus Importer:2022-12-16
Keywords: beam manipulation; laser application; laser dynamics; laser source; novel laser development

Effective Negative Nonlinearity of a Nonlinear Amplifying Loop Mirror for Compensating Nonlinearity-Incuced Signal Distortions - Sponsel, Klaus; Cvecek, Kristian; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Optical Communication, 2008. ECOC 2008. 34th European Conference on 21-25, 2008)
UnivIS-Import:2017-12-18:Pub.2008.tech.IE.LEH.effect

Effect of Amplitude Noise on Multi-Level Phase Regeneration - Lenz, M.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (Lasers and Electro-Optics Europe (CLEO EUROPE/EQEC), 2011 Conference on and 12th European Quantum Electronics Conference, 2011)
lhft_intern.bib::Lenz2011

Effect of dimensionality on the spectra of hybrid plasmonic-photonic crystals - Romanova, Alexandra; Korovin, A. V.; Romanov, Sergey (Physics of the Solid State, 2013)
Based on colloidal crystals of various dimensionality, hybrid metal-dielectric plasmonic-photonic heterocrystals have been prepared. It has been shown that the spectra of optical transmission of heterocrystals are mostly controlled by the sum of contributions of composing plasmonic and photonic crystals. At the same time, there are a number of phenomena caused by the mutual effect of heterostructure components, which lead to a deviation of observed optical properties from the linear superposition of responses of these crystals. In particular, it has been found that the anomalous transmission controlled by the plasmonic crystal decreases with increasing the dimensionality of the photonic crystal attached to it. At the same time, light reflection on a metallized surface changes light diffraction in photonic crystals and leads to Fabry-Perot oscillation amplification. It has been assumed that an intermediate layer is formed, in which Bloch modes of the photonic crystal and surface plasmon-polaritons of the plasmonic crystal are hybridized.
EAM Import::2019-03-14

Effect of fabrication errors on the diffraction pattern produced by sawtooth gratings - Harder, Irina; Lindlein, Norbert; Torcall-Milla, Francisco Jose (Applied Optics, 2010)

Effect of rapid thermal annealing on barrier height and 1/f noise of Ni/GaN Schottky barrier diodes - Kumar, Ashutosh; Latzel, Michael; Christiansen, Silke; Kumar, V.; Singh, R. (Applied Physics Letters, 2015)
Current-voltage (as a function of temperature), capacitance-voltage, and 1/f noise characteristics of Ni/GaN Schottky barrier diodes (SBDs) as function of rapid thermal annealing (RTA) are studied. It is found that RTA treatments of SBDs at 450 °C for 60 s resulted in a significant improvement of ideality factor and Schottky barrier height: the ideality factor decreased from 1.79 to 1.12 and the barrier height increased from 0.94 to 1.13 eV. The spectral power density of current fluctuations in the diode subjected to RTA at 450 °C is found to be two orders of magnitude lower as compared to the as-deposited diode. Improved diode characteristics and decreased 1/f noise in RTA treated (450 °C/60 s) diode are attributed to reduced level of barrier inhomogeneities at the metal-semiconductor interface and explained within the framework of the spatial inhomogeneity model.
EAM Import::2019-03-14

Efficient chirp-assisted SRS in H2-filled hollow-core PCF for generation of ultrashort LP01 pulses at 1.8 μm - Loranger, Sebastien; Novoa, David; Russell, Philip St. John (Optics InfoBase Conference Papers, 2020)
Sub-40 fs pulses at 1.8 µm are generated by pumping H2-filled hollow-core PCF with 300 fs, 1.03 µm fiber laser pulses pre-chirped to a duration of 640 fs. Conversion efficiencies of 50% are obtained.
CRIS-Team Scopus Importer:2020-11-13

Efficient coupling to an optical resonator by exploiting time-reversal symmetry - Bader, Marianne; Heugel, Simon Tobias; Chekhov, Alexander; Sondermann, Markus; Leuchs, Gerd (New Journal of Physics, 2013)
The interaction of a cavity with an external field is symmetric under time reversal. Thus, coupling to a resonator is most efficient when the incident light is the time reversed version of a free cavity decay, i.e. when it has a rising exponential shape matching the cavity lifetime. For light entering the cavity from only one side, the maximally achievable coupling efficiency is limited by the choice of the cavity mirrors' reflectivities. Such an empty-cavity experiment serves also as a model system for single-photon single-atom absorption dynamics. We present experiments coupling exponentially rising pulses to a cavity system which allows for high coupling efficiencies. The influence of the time constant of the rising exponential is investigated as well as the effect of a finite pulse duration. We demonstrate coupling 94% of the incident TEM mode into the resonator. © IOP Publishing and Deutsche Physikalische Gesellschaft.

Efficient generation of temporally shaped photons using nonlocal spectral filtering - Averchenko, Valentin; Sych, Denis; Marquardt, Christoph; Leuchs, Gerd (Physical Review A, 2020)
We study the generation of single-photon pulses with the tailored temporal shape via nonlocal spectral filtering. A shaped photon is heralded from a time-energy entangled photon pair upon spectral filtering and time-resolved detection of its entangled counterpart. We show that the temporal shape of the heralded photon is defined by the time-inverted impulse response of the spectral filter and does not depend on the heralding instant. Thus one can avoid postselection of particular heralding instants and achieve a substantially higher heralding rate of shaped photons as compared to the generation of photons via nonlocal temporal modulation. Furthermore, the method can be used to generate shaped photons with a coherence time in the ns-mu s range and is particularly suitable to produce photons with the exponentially rising temporal shape required for efficient interfacing to a single quantum emitter in free space.
CRIS-Team WoS Importer:2020-01-24

Efficient microwave to optical photon conversion: An electro-optical realization - Rueda, Alfredo; Sedlmeir, Florian; Collodo, Michele; Vogl, Ulrich; Stiller, Birgit; Schunk, Gerhard; Strekalov, Dmitry V.; Marquardt, Christoph; Fink, Johannes M.; Painter, Oskar; Leuchs, Gerd; Schwefel, Harald G. L. (Optica, 2016)
Linking classical microwave electrical circuits to the optical telecommunication band is at the core of modern communication. Future quantum information networks will require coherent microwave-to-optical conversion to link electronic quantum processors and memories via low-loss optical telecommunication networks. Efficient conversion can be achieved with electro-optical modulators operating at the single microwave photon level. In the standard electro-optic modulation scheme, this is impossible because both up- and down-converted sidebands are necessarily present. Here, we demonstrate true single-sideband up- or down-conversion in a triply resonant whispering gallery mode resonator by explicitly addressing modes with asymmetric free spectral range. Compared to previous experiments, we show a 3 orders of magnitude improvement of the electro-optical conversion efficiency, reaching 0.1% photon number conversion for a 10 GHz microwave tone at 0.42 mW of optical pump power. The presented scheme is fully compatible with existing superconducting 3D circuit quantum electrodynamics technology and can be used for nonclassical state conversion and communication. Our conversion bandwidth is larger than 1 MHz and is not fundamentally limited.
CRIS-Team Scopus Importer:2021-06-29

Efficient Nitrogen Doping of Single-Layer Graphene Accompanied by Negligible Defect Generation for Integration into Hybrid Semiconductor Heterostructures - Sarau, George; Heilmann, Martin; Bashouti, Muhammad; Latzel, Michael; Tessarek, Christian; Christiansen, Silke (ACS Applied Materials and Interfaces, 2017)
While doping enables application-specific tailoring of graphene properties, it can also produce high defect densities that degrade the beneficial features. In this work, we report efficient nitrogen doping of ∼11 atom % without virtually inducing new structural defects in the initial, large-area, low defect, and transferred single-layer graphene. To shed light on this remarkable high-doping–low-disorder relationship, a unique experimental strategy consisting of analyzing the changes in doping, strain, and defect density after each important step during the doping procedure was employed. Complementary micro-Raman mapping, X-ray photoelectron spectroscopy, and optical microscopy revealed that effective cleaning of the graphene surface assists efficient nitrogen incorporation accompanied by mild compressive strain resulting in negligible defect formation in the doped graphene lattice. These original results are achieved by separating the growth of graphene from its doping. Moreover, the high doping level occurred simultaneously with the epitaxial growth of n-GaN micro- and nanorods on top of graphene, leading to the flow of higher currents through the graphene/n-GaN rod interface. Our approach can be extended toward integrating graphene into other technologically relevant hybrid semiconductor heterostructures and obtaining an ohmic contact at their interfaces by adjusting the doping level in graphene.
EAM Import::2019-03-14

Efficient optical up-conversion by coherent sum-frequency generation for highly sensitive terahertz detection - Sedlmeir, Florian; Schwefel, Harald; Strekalov, Dmitry V.; Bauerschmidt, Sebastian; Preu, Sascha; Malzer, Stefan; Döhler, Gottfried; Leuchs, Gerd (2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011, 2011)
Detection of weak THz signals is very challenging due to the extremely low energy of one THz photon (temperature equivalent of 48K). Frequency up-conversion to the near infra-red (NIR) and subsequent detection of the up-converted photon with sensitive, low-noise detectors is one way to achieve this task, albeit suffering form extremely poor conversion rates. Whispering gallery mode resonators (WGMRs), however, support well confined modes with high quality factors (Q) and extremely high field intensities inside the resonator, thus allowing efficient non-linear conversion rates. © 2011 IEEE.

Efficient polarization squeezing in optical fibers - Leuchs, Gerd; et al. (Optics Letters, 2005)
UnivIS-Import:2015-03-09:Pub.2005.nat.dphy.optik.1optik.effici

Efficient saturation of an ion in free space - Fischer, Martin; Bader, Marianne; Maiwald, Robert; Golla, Andrea; Sondermann, Markus; Leuchs, Gerd (Applied Physics B-Lasers and Optics, 2014)
We report on the demonstration of a light-matter interface coupling light to a single (Formula presented.) ion in free space. The interface is realized through a parabolic mirror partially surrounding the ion. It transforms a Laguerre–Gaussian beam into a linear dipole wave converging at the mirror’s focus. By measuring the non-linear response of the atomic transition, we deduce the power required for reaching an upper-level population of (Formula presented.) to be (Formula presented.) at half linewidth detuning from the atomic resonance. Performing this measurement while scanning the ion through the focus provides a map of the focal intensity distribution. From the measured power, we infer a coupling efficiency of (Formula presented.) on the linear dipole transition when illuminating from half solid angle, being among the best coupling efficiencies reported for a single atom in free space.

Efficient self-compression of ultrashort near-UV pulses in air-filled hollow-core photonic crystal fibers - Luan, Jie; Russell, Philip St. John; Novoa, David (Optics Express, 2021)
We report generation of ultrashort near-UV pulses by soliton self-compression in kagomé-style hollow-core photonic crystal fibers filled with ambient air. Pump pulses with the energy of 2.6 μJ and duration of 54 fs at 400 nm were compressed temporally by a factor of 5, to a duration of ∼11 fs. The experimental results are supported by numerical simulations, showing that both Raman and Kerr effects play a role in the compression dynamics. The convenience of using ambient air and the absence of glass windows that would distort the compressed pulses makes the setup highly attractive as the basis of an efficient table-top UV pulse compressor.
CRIS-Team Scopus Importer:2021-05-14

Efficient single sideband microwave to optical conversion using a LiNbO3 WGM-resonator - Rueda, Alfredo; Sedlmeir, Florian; Collodo, Michele; Vogl, Ulrich; Stiller, Birgit; Schunk, Gerhard; Strekalov, Dimitry V.; Marquardt, Christoph; Fink, Johannes M.; Painter, Oskar; Leuchs, Gerd; Schwefel, Harald G.L. (2016 Conference on Lasers and Electro-Optics, CLEO 2016, 2016)
We present a coherent microwave to telecom signal converter based on the electro-optical effect using a crystalline WGM-resonator coupled to a 3D microwave cavity, achieving high photon conversion efficiency of 0.1% with MHz bandwidth.
CRIS-Team Scopus Importer:2021-06-29

Efficient terahertz emission from ballistic transport enhanced n-i-p-n-i-p superlattice photomixers - Preu, Sascha; Renner, Frank; Malzer, Stefan; Döhler, Gottfried; Wang, Lijun; Hanson, Micah; Gossard, Art; Wilkinson, T.L.J.; Brown, Elliott R. (Applied Physics Letters, 2007)
The authors report on photomixing terahertz sources that overcome the transit time versus RC -time trade-off and allow for independent optimization of both of them, using a n-i-p-n-i-p superlattice. Furthermore, they take advantage of ballistic transport for reduced transit times. Apart from more favorable material parameters, In(Al)GaAs photomixers benefit from the advanced telecommunication laser technology around 1.55 μm as compared to GaAs. In such devices, a terahertz-power output of 1 μW has been achieved at 0.4 THz at a photocurrent of 3.8 mA. A comparison between corresponding GaAs- and InGaAs-based n-i-p-n-i-p photomixers reveals an improvement of performance by at least an order of magnitude for the latter one. © 2007 American Institute of Physics.

Effiziente Berechnung der Impulsantwort zeitabhängiger Signale in gedruckten Polymer Optischen Wellenleitern (POWs) - Backhaus, Carsten; Loosen, Florian; Lindlein, Norbert (Proceeding, 118. DGaO-Jahrestagung, 2017)
Gedruckte Polymer optische Wellenleiter (POWs) sind hochgradig multimodig, sodass eine Raytracing Simulation mit guter Näherung verwendet werden darf. Neben der Erweiterung des Simulationsmodells von Wellenleitern bezüglich der Dämpfung des Signals [1] wurde eine Erweiterung bezüglich der Signaldispersion eingeführt. Für diese wurde ein effizientes Verfahren entwickelt, welches für die Anwendung auf POWs optimiert ist, indem die speziellen physikalischen Eigenschaften dieser ausgenutzt werden. Erste Ergebnisse aus den Simulationen werden hier präsentiert. Die Effizienz resultiert aus der Annahme, dass die Signallaufzeit t eines Strahls als Verhältnis der Weglänge und der Lichtgeschwindigkeit c/n im Medium berechnet werden kann. Abhängig von der Mode des Strahls, wird er im Strahlenmodell unterschiedliche Weglängen zurücklegen. Indem man alle Strahlen vom Sender zum Detektor nach ihrer Signallaufzeit ordnet und in kleine Laufzeitintervalle Δt einteilt, kann man die Strahlleistung aller Strahlen innerhalb eines Laufzeitintervalls aufsummieren, und erhält die Impulsantwort des Systems direkt durch eine Raytracing Simulation. [1] F. Loosen et al. DGaO Proceedings C5 (2016)

Eine neue Methode zur Abformung sensibler Objekte - Häusler, Gerd; et al. (Restauro, 2001)
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.optik.1optik.einene

Electrical circuit model of arrays of resonant elements - Lomanets, Vadym; Zhuromskyy, Oleksandr; Onishchukov, G.; Peschel, Ulf (Physical Review B, 2012)
We present an effective electrical circuit model that can be used for a quasianalytic analysis of electromagnetic oscillations in arrays of coupled elements, resonant in the microwave domain. The model accounts for electric and magnetic interactions between charges and currents excited in individual resonators. Respective coupling coefficients can be calculated from the field and current distributions in a subsystem of just one or two elements, provided by a finite-difference electromagnetic solver. The model was used to investigate current distributions and dispersion relations of wave propagation on chains of coupled split-ring resonators. The change of the dispersion characteristics from forward to backward propagating wave type observed experimentally is readily reproduced by the model.
EAM Import::2019-03-14

Electronic noise-free measurements of squeezed light - Leuchs, Gerd; et al. (Optics Letters, 2008)
We study the implementation of a correlation measurement technique for the characterization of squeezed light. We show that the sign of the covariance coefficient revealed from the time-resolved correlation data allow us to distinguish among squeezed, coherent, and thermal states. In contrast to the traditional method of characterizing squeezed light, involving measurement of the variation of the difference photocurrent, the correlation measurement method allows one to eliminate the contribution of the electronic noise, which becomes a crucial issue in experiments with dim sources of squeezed light. © 2008 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2008.nat.dphy.optik.1optik.electr

Electro-optic frequency comb generation in lithium niobate whispering gallery mode resonators - Rueda, Alfredo; Sedlmeir, Florian; Leuchs, Gerd; Kuamri, Madhuri; Schwefel, Harald G.L. (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Optical frequency combs (OFCs) are light sources whose spectra consists of equally spaced frequency lines in the optical domain [1]. They have great potential for improving high-capacity data transfer, all-optical atomic clocks, spectroscopy, and high-precision measurements [2].
CRIS-Team Scopus Importer:2019-11-15

Emission of circularly polarized light by a linear dipole - Neugebauer, Martin; Banzer, Peter; Nechayev, Sergey (Science Advances, 2019)
Controlling the polarization state and the propagation direction of photons is a fundamental prerequisite for many nanophotonic devices and a precursor for future on-chip communication, where the emission properties of individual emitters are particularly relevant. Here, we report on the emission of partially circularly polarized photons by a linear dipole. The underlying effect is linked to the near-field part of the angular spectrum of the dipole, and it occurs in any type of linear dipole emitter, ranging from atoms and quantum dots to molecules and dipole-like antennas. We experimentally observe it by near-field to far-field transformation at a planar dielectric interface and numerically demonstrate the utility of this phenomenon by coupling the circularly polarized light to the individual paths of crossing waveguides.
CRIS-Team Scopus Importer:2019-07-09

Emission of semiconductor nanocrystals in photonic crystal environment - Romanov, Sergey; Peschel, Ulf (Nanocrystals: Synthesis, Properties and Applications, 2010)
EAM Import::2019-03-14

Empirical Strategy forDetection and Removal of Misalignment Aberrations inInterferometry - Lindlein, Norbert; et al. (Optik, 2001)
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.optik.1optik.empiri

Encapsulation of silver nanowire networks by atomic layer deposition for indium-free transparent electrodes - Göbelt, Manuela; Keding, Ralf; Schmitt, Sebastian W.; Hoffmann, Bjoern; Jaeckle, Sara; Latzel, Michael; Radmilovic, Vuk V.; Radmilovic, Velimir R.; Spiecker, Erdmann; Christiansen, Silke; Hoffmann, Björn (Nano Energy, 2015)
We report on the development of a novel nano-composite transparent electrode material to be used in various energy applications e.g. as contacts for solar cells, composed of a wet-chemically synthesized silver nanowire (AgNW) network encapsulated in a transparent conductive oxide (TCO) which was deposited with nano-scale precision by atomic layer deposition (ALD). The AgNWs form a random network on a substrate of choice when being drop casted. ALD encapsulation of AgNWs guarantees a conformal and thickness controlled coating of the wires e.g. by the selected aluminum doped zinc oxide (AZO). Annealing of the AgNWs prior to ALD coating, yield a local sintering of AgNWs at their points of intersection, which improves the conductivity of the composite electrodes by reducing their sheet resistance. To demonstrate the performance of these AgNW/AZO composite transparent electrodes, they were used as a top electrode on wafer-based silicon (Si) - solar cells. A novel combination of scanning electron microscopy and image processing is used to determine the degree of percolation of the AgNWs on large areas of the nano-composite AgNW/AZO electrodes. Our results show that the solar cell with percolated AgNW/AZO electrode show the highest short circuit current density (28 mA/cm(2)) and a series resistance in the same order of magnitude compared to reference solar cells with a thermally evaporated silver grid electrode. The electrode example we chose reveals that the developed AgNW/AZO electrode is a technologically relevant and cheap alternative to conventional solar cell screen printed grid electrodes, which contain similar to 95% more Ag per device area, with a high potential to be further systematically optimized by the presented image processing method. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: Atomic layer deposition; Silver nano wires; Transparent electrode; Encapsulation; Aluminum doped zinc oxide (AZO); Solar cell

Engineered disorder and light propagation in a planar photonic glass - Romanov, Sergey; Orlov, Sergej; Ploss, Daniel; Weiss, Clemens K.; Vogel, Nicolas; Peschel, Ulf (Scientific Reports, 2016)
The interaction of light with matter strongly depends on the structure of the latter at wavelength scale. Ordered systems interact with light via collective modes, giving rise to diffraction. In contrast, completely disordered systems are dominated by Mie resonances of individual particles and random scattering. However, less clear is the transition regime in between these two extremes, where diffraction, Mie resonances and near-field interaction between individual scatterers interplay. Here, we probe this transitional regime by creating colloidal crystals with controlled disorder from two-dimensional self-assembly of bidisperse spheres. Choosing the particle size in a way that the small particles are transparent in the spectral region of interest enables us to probe in detail the effect of increasing positional disorder on the optical properties of the large spheres. With increasing disorder a transition from a collective optical response characterized by diffractive resonances to single particles scattering represented by Mie resonances occurs. In between these extremes, we identify an intermediate, hopping-like light transport regime mediated by resonant interactions between individual spheres. These results suggest that different levels of disorder, characterized not only by absence of long range order but also by differences in short-range correlation and interparticle distance, exist in colloidal glasses.

Engineered Light Scattering in Colloidal Photonic Heterocrystals - Ding, Boyang; Bardosova, Maria; Povey, Ian; Pemble, Martyn E.; Romanov, Sergei G. (Advanced Functional Materials, 2010)
Photonic heterocrystals are prepared by sandwiching films of self-assembled opal and force-assembled Langmuir–Blodgett colloidal crystals. Anomalously strong light scattering in conjunction with low reflectivity is observed with increasing angle of incidence in the spectral range of photonic bandgaps. The occurrence of light scattering at the interface has been assigned to the optical mode mismatch between the two types of photonic crystals. Photonic bandgap-related mechanisms of trapping the decaying photonic crystal modes at the interface are suggested.
EAM Import::2019-03-14

Engineering Long-Lived Vibrational States for an Organic Molecule - Gurlek, Burak; Sandoghdar, Vahid; Martin-Cano, Diego (Physical Review Letters, 2021)
The optomechanical character of molecules was discovered by Raman about one century ago. Today, molecules are promising contenders for high-performance quantum optomechanical platforms because their small size and large energy-level separations make them intrinsically robust against thermal agitations. Moreover, the precision and throughput of chemical synthesis can ensure a viable route to quantum technological applications. The challenge, however, is that the coupling of molecular vibrations to environmental phonons limits their coherence to picosecond time scales. Here, we improve the optomechanical quality of a molecule by several orders of magnitude through phononic engineering of its surrounding. By dressing a molecule with long-lived high-frequency phonon modes of its nanoscopic environment, we achieve storage and retrieval of photons at millisecond timescales and allow for the emergence of single-photon strong coupling in optomechanics. Our strategy can be extended to the realization of molecular optomechanical networks.
CRIS-Team Scopus Importer:2021-10-01

Engineering of spontaneous emission in free space via conditional measurements - Bojer, Manuel; Götzendörfer, Lukas; Bachelard, Romain; von Zanthier, Joachim (Physical Review Research, 2022)
We study the collective spontaneous emission of three identical two-level atoms initially prepared in the excited states by measuring Glauber's third-order photon correlation function. Assuming two atoms at subwavelength distance from each other such that they are subject to the dipole-dipole interaction while the third one is located several wavelengths away, we observe super- and subradiant decay alike, depending on the direction of observation. Unlike the case where no remote atom is introduced or no conditional measurements are performed, the spontaneous emission behavior of the conditioned three-atom system is strongly modified, i.e., differing from the single-atom and the canonical two-atom configuration. The conditional measurements associated with the three-photon correlation function in combination with the dipole-dipole interaction between the adjacent atoms lead to quantum interference among the different decay channels allowing one to engineer the spontaneous emission in space and time.
CRIS-Team Scopus Importer:2022-10-21

Enhanced free space beam capture by improved optical tapers - Bartley, Tim; Heim, Bettina; Elser, Dominique Alexander; Sych, Denis; Sabuncu, Metin; Wittmann, Christoffer; Lindlein, Norbert; Marquardt, Christoph; Leuchs, Gerd (2010)
In our continuous variable quantum key distribution (QKD) scheme, the homodyne detection set-up requires balancing the intensity of an incident beam between two photodiodes. Realistic lens systems are insufficient to provide a spatially stable focus in the presence of large spatial beam-jitter caused by atmospheric transmission. We therefore present an improved geometry for optical tapers which offer up to four times the angular tolerance of a lens. The effective area of a photodiode can thus be increased, without decreasing its bandwidth. This makes them suitable for use in our free space QKD experiment and in free space optical communication in general. © Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering 201
Keywords: Atmospheric optics; Beam-jitter; Free space communication; Optical taper; Quantum key distribution; Random media

Enhanced spin-orbit coupling in an epsilon-near-zero material - Eismann, Jörg; Ackermann, Lisa; Kantor, Brian; Nechayev, Sergey; Alam, M. Zahirul; Fickler, Robert; Boyd, Robert W.; Banzer, Peter (Optica, 2022)
Light can carry both spin and orbital angular momentum. While it is known that a nonparaxial circularly polarized beam couples the spin angular momentum to orbital angular momentum, this phenomenon does not hold upon col-limation of the field. With the rising interest in epsilon-near-zero photonics, integral ingredients to this field are the beam-shaping capabilities of such a regime. In this work, it is experimentally shown that a permanent conversion of spin-to-orbital angular momentum arises naturally from an incident circularly polarized field on an isotropic inter-face due to the asymmetry in the Fresnel coefficients. More significantly, the conversion efficiency can be substantially enhanced in the presence of an epsilon-near-zero film due to the unique Fresnel properties exhibited in such a regime. It is further shown that the conversion efficiency scales with the nonparaxiality of the incident field. Our study showcases the intriguing phenomena resulting from the combination of concepts as old as Fresnel coefficients and modern mate-rials such as epsilon-near-zero films. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
CRIS-Team WoS Importer:2022-10-21

Ensemble-Induced Strong Light-Matter Coupling of a Single Quantum Emitter - Schutz, S.; Schachenmayer, J.; Hagenmuller, D.; Brennen, G. K.; Volz, Thomas; Sandoghdar, Vahid; Ebbesen, T. W.; Genes, C.; Pupillo, G. (Physical Review Letters, 2020)
We discuss a technique to strongly couple a single target quantum emitter to a cavity mode, which is enabled by virtual excitations of a nearby mesoscopic ensemble of emitters. A collective coupling of the latter to both the cavity and the target emitter induces strong photon nonlinearities in addition to polariton formation, in contrast to common schemes for ensemble strong coupling. We demonstrate that strong coupling at the level of a single emitter can be engineered via coherent and dissipative dipolar interactions with the ensemble, and provide realistic parameters for a possible implementation with SiV- defects in diamond. Our scheme can find applications, amongst others, in quantum information processing or in the field of cavity-assisted quantum chemistry.
CRIS-Team WoS Importer:2020-04-10

Entangled photons from subwavelength nonlinear films - Santiago-Cruz, Tomas; Sultanov, Vitaliy; Zhang, Haizhong; Krivitsky, Leonid A.; Chekhova, Maria (Optics Letters, 2021)
Miniaturized entangled photon sources, in particular based on subwavelength metasurfaces, are highly demanded for the development of integrated quantum photonics. Here, as a first step towards the development of quantum optical metasurfaces (QOMs), we demonstrate generation of entangled photons via spontaneous parametric down-conversion (SPDC) from subwavelength films. We achieve photon pair generation with a high coincidence-to-accidental ratio in lithium niobate and gallium phosphide nanofilms. By implementing the fiber spectroscopy of SPDC in nanofilms, we measure a spectrum with a bandwidth of 500 nm, limited only by the overall detection efficiency. The spectrum reveals vacuum field enhancement due to a Fabry-Perot resonance inside the nonlinear films. It also suggests a strategy for observing SPDC from QOM. Our experiments lay the groundwork for future development of flat SPDC sources, including QOM. (C) 2021 Optical Society of America
CRIS-Team WoS Importer:2021-03-19

Entanglement of Gaussian states and the applicability to quantum key distribution over fading channels - Usenko, Vladyslav C.; Heim, Bettina; Peuntinger, Christian; Wittmann, Christoffer; Marquardt, Christoph; Leuchs, Gerd; Filip, Radim (New Journal of Physics, 2012)
Entanglement properties of Gaussian states of light as well as the security of continuous variable quantum key distribution with Gaussian states in free-space fading channels are studied. These qualities are shown to be sensitive to the statistical properties of the transmittance distribution in the cases when entanglement is strong or when channel excess noise is present. Fading, i.e. transmission fluctuations, caused by beam wandering due to atmospheric turbulence, is a frequent challenge in free-space communication. We introduce a method of fading discrimination and subsequent post-selection of the corresponding sub-states and show that it can improve the entanglement resource and restore the security of the key distribution over a realistic fading link. Furthermore, the optimal post-selection strategy in combination with an optimized entangled resource is shown to drastically increase the protocol's robustness to excess noise, which is confirmed for experimentally measured fading channel characteristics. The stability of the result against finite data ensemble size and imperfect channel estimation is also addressed. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
CRIS-Team Scopus Importer:2022-06-05

Entanglement of polarization and orbital angular momentum - Bhatti, Daniel; von Zanthier, Joachim; Agarwal, G. S. (Physical Review A, 2015)
We investigate two-photon entangled states using two important degrees of freedom of the electromagnetic field, namely orbital angular momentum (OAM) and spin angular momentum. For photons propagating in the same direction we apply the idea of entanglement duality and develop schemes to do entanglement sorting based on either OAM or polarization. In each case the entanglement is tested using appropriate witnesses. We finally present generalizations of these ideas to three-and four-photon entangled state

Entanglement Stabilization in a Superconducting Quantum Processor using Parity Detection and Real-Time Feedback - Eichler, Christopher (Workshop on Machine Learning for Quantum Technology, 2019)

Entangling different degrees of freedom by quadrature squeezing cylindrically polarized modes - Gabriel, C.; Aiello, Andrea; Zhong, W.; Euser, T. G.; Joly, N. Y.; Banzer, Peter; Foertsch, M.; Elser, Dominique; Andersen, U. L.; Marquardt, Christoph; Russell, P. St. J.; Leuchs, Gerd (Physical Review Letters, 2011)
Quantum systems such as, for example, photons, atoms, or Bose-Einstein condensates, prepared in complex states where entanglement between distinct degrees of freedom is present, may display several intriguing features. In this Letter we introduce the concept of such complex quantum states for intense beams of light by exploiting the properties of cylindrically polarized modes. We show that already in a classical picture the spatial and polarization field variables of these modes cannot be factorized. Theoretically it is proven that by quadrature squeezing cylindrically polarized modes one generates entanglement between these two different degrees of freedom. Experimentally we demonstrate amplitude squeezing of an azimuthally polarized mode by exploiting the nonlinear Kerr effect in a specially tailored photonic crystal fiber. These results display that such novel continuous-variable entangled systems can, in principle, be realized.© 2011 American Physical Society.
CRIS-Team Scopus Importer:2022-06-05

Entangling Fiber Solitons - Quantum Noise Engineering for Interferometry and Communication - Leuchs, Gerd; et al. (Optics and Photonics News, 2002)
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.entang

Entangling the Whole by Beam Splitting a Part - Croal, Callum; Peuntinger, Christian; Chille, Vanessa; Marquardt, Christoph; Leuchs, Gerd; Korolkova, Natalia; Mista, Ladislav (Physical Review Letters, 2015)
A beam splitter is a basic linear optical element appearing in many optics experiments and is frequently used as a continuous-variable entangler transforming a pair of input modes from a separable Gaussian state into an entangled state. However, a beam splitter is a passive operation that can create entanglement from Gaussian states only under certain conditions. One such condition is that the input light is suitably squeezed. We demonstrate, experimentally, that a beam splitter can create entanglement even from modes which do not possess such a squeezing provided that they are correlated to, but not entangled with, a third mode. Specifically, we show that a beam splitter can create three-mode entanglement by acting on two modes of a three-mode fully separable Gaussian state without entangling the two modes themselves. This beam splitter property is a key mechanism behind the performance of the protocol for entanglement distribution by separable states. Moreover, the property also finds application in collaborative quantum dense coding in which decoding of transmitted information is assisted by interference with a mode of the collaborating party.
CRIS-Team Scopus Importer:2022-06-05

Environment-assisted quantum-information correction for continuous variables - Leuchs, Gerd; Andersen, Ulrik Lund; et al. (Physical Review A, 2010)
Quantum-information protocols are inevitably affected by decoherence which is associated with the leakage of quantum information into an environment. In this article we address the possibility of recovering the quantum information from an environmental measurement. We investigate continuous-variable quantum information, and we propose a simple environmental measurement that under certain circumstances fully restores the quantum information of the signal state although the state is not reconstructed with unit fidelity. We implement the protocol for which information is encoded into conjugate quadratures of coherent states of light and the noise added under the decoherence process is of Gaussian nature. The correction protocol is tested using both a deterministic as well as a probabilistic strategy. The potential use of the protocol in a continuous-variable quantum-key distribution scheme as a means to combat excess noise is also investigated. © 2010 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2010.nat.dphy.optik.1optik.enviro

Epithelial RAC1-dependent cytoskeleton dynamics controls cell mechanics, cell shedding and barrier integrity in intestinal inflammation - Martínez Sánchez, Luz del Carmen; Phuong Anh Ngo,; Pradhan, Rashmita; Becker, Lukas S; Böhringer, David; Soteriou, Despina; Kubankova, Marketa; Schweitzer, Christine; Koch, Tatyana; Thonn, Veronika; Erkert, Lena; Stolzer, Iris; et al. (Gut, 2022)
Objective Increased apoptotic shedding has been linked to intestinal barrier dysfunction and development of inflammatory bowel diseases (IBD). In contrast, physiological cell shedding allows the renewal of the epithelial monolayer without compromising the barrier function. Here, we investigated the role of live cell extrusion in epithelial barrier alterations in IBD. Design Taking advantage of conditional GGTase and RAC1 knockout mice in intestinal epithelial cells (Pggt1b (i Delta IEC) and Rac1 (i Delta IEC) mice), intravital microscopy, immunostaining, mechanobiology, organoid techniques and RNA sequencing, we analysed cell shedding alterations within the intestinal epithelium. Moreover, we examined human gut tissue and intestinal organoids from patients with IBD for cell shedding alterations and RAC1 function. Results Epithelial Pggt1b deletion led to cytoskeleton rearrangement and tight junction redistribution, causing cell overcrowding due to arresting of cell shedding that finally resulted in epithelial leakage and spontaneous mucosal inflammation in the small and to a lesser extent in the large intestine. Both in vivo and in vitro studies (knockout mice, organoids) identified RAC1 as a GGTase target critically involved in prenylation-dependent cytoskeleton dynamics, cell mechanics and epithelial cell shedding. Moreover, inflamed areas of gut tissue from patients with IBD exhibited funnel-like structures, signs of arrested cell shedding and impaired RAC1 function. RAC1 inhibition in human intestinal organoids caused actin alterations compatible with arresting of cell shedding. Conclusion Impaired epithelial RAC1 function causes cell overcrowding and epithelial leakage thus inducing chronic intestinal inflammation. Epithelial RAC1 emerges as key regulator of cytoskeletal dynamics, cell mechanics and intestinal cell shedding. Modulation of RAC1 might be exploited for restoration of epithelial integrity in the gut of patients with IBD.
CRIS-Team WoS Importer:2022-03-25

Erratum: Lattice-plasmon-induced asymmetric transmission in two-dimensional chiral arrays (APL Photonics (2022) 7 (016105) DOI: 10.1063/5.0074849) - Apurv Chaitanya, N.; Butt, M. A. T.; Reshef, O.; Boyd, Robert W.; Banzer, Peter; De Leon, Israel (APL Photonics, 2022)
The original article1 contains an error in Eq. (1). The correct equation is. (Formula Presented) The original article’s analysis, findings, and conclusions remain the same.
CRIS-Team Scopus Importer:2022-10-14

Estimation of the mass density of biological matter from refractive index measurements - Möckel, Conrad; Beck, Timon; Abuhattum, Shada; Kim, Kyoohyun; Kolb, Julia; Wehner, Daniel; Zaburdaev, Vasily; Guck, Jochen; et al. (Biophysical Reports, 2024)
The quantification of physical properties of biological matter gives rise to novel ways of understanding functional mechanisms. One of the basic biophysical properties is the mass density (MD). It impacts the dynamics in sub-cellular compartments and plays a major role in defining the opto-acoustical properties of cells and tissues. As such, the MD can be connected to the refractive index (RI) via the well known Lorentz–Lorenz relation, which takes into account the polarizability of matter. However, computing the MD based on RI measurements poses a challenge, as it requires detailed knowledge of the biochemical composition of the sample. Here we propose a methodology on how to account for assumptions about the biochemical composition of the sample and respective RI measurements. To this aim, we employ the Biot mixing rule of RIs alongside the assumption of volume additivity to find an approximate relation of MD and RI. We use Monte–Carlo simulations and Gaussian propagation of uncertainty to obtain approximate analytical solutions for the respective uncertainties of MD and RI. We validate this approach by applying it to a set of well-characterized complex mixtures given by bovine milk and intralipid emulsion and employ it to estimate the MD of living zebrafish (Danio rerio) larvae trunk tissue. Our results illustrate the importance of implementing this methodology not only for MD estimations but for many other related biophysical problems, such as mechanical measurements using Brillouin microscopy and transient optical coherence elastography.<br
Keywords: Mass density; Refractive index; Optical diffraction tomography; Brillouin microscopy; Optical coherence elastography

Etched microlenses for Optical Systems - Lindlein, Norbert; et al. (EOS Topical Meetings Digest Series, 1998)
UnivIS-Import:2015-03-05:Pub.1998.nat.dphy.optik.1optik.etched

Evading Vacuum Noise: Wigner Projections or Husimi Samples? - Mueller, C. R.; Peuntinger, Christian; Dirmeier, T.; Khan, Imran; Vogl, Ulrich; Marquardt, Christoph; Leuchs, Gerd; Sanchez-Soto, L. L.; Teo, Y. S.; Hradil, Zdenek; Rehacek, Jaroslav (Physical Review Letters, 2016)
The accuracy in determining the quantum state of a system depends on the type of measurement performed. Homodyne and heterodyne detection are the two main schemes in continuous-variable quantum information. The former leads to a direct reconstruction of the Wigner function of the state, whereas the latter samples its Husimi Q function. We experimentally demonstrate that heterodyne detection outperforms homodyne detection for almost all Gaussian states, the details of which depend on the squeezing strength and thermal noise.
CRIS-Team Scopus Importer:2022-06-05

Evaluation algorithms for multistep measurement of spatially varying linear polarization and phase - Berger, Andreas; Nercissian, Vanusch; Mantel, Klaus Peter; Harder, Irina (Optics Letters, 2012)

Evaluation of 4H-SiC MOSFET transfer characteristics using machine-learning techniques - Lehmeyer, Johannes; Citak, Timon; Weber, Heiko B.; Krieger, Michael (Electronics Letters, 2023)

Excitation of gap plasmonic wavguides by nano antennas - Schmauß, Bernhard; Weng, J.; Banzer, P.; Ploss, D.; Kriesch, A.; Peschel, Ulf (Conference on Lasers and Electro-Optics CLEO, Paper QMF1, San Jose, May, 2010)
We experimentally demonstrate the excitation of plasmonic gap waveguides by nano antennas. The excitation is shown to be both spatially and spectrally dependent which can potentially be used for the selective excitation of plasmonic nanostructure
lhft_intern.bib::Schmauss10

Excitation of plasmonic gap waveguides by nanoantennas - Romanov, Sergey; et al. (Optics Express, 2009)
We model and optimize the excitation of a plasmonic gap waveguide by a dipole antenna. The coupling efficiency strongly depends on antenna and waveguide properties where impedanec matching plays a critical role. The optimization of antenna lengths and gap widths shows that concepts of circuit networks can likewise be applied to optical frequencies. Using classical optimization schemes known from electrical engineering we manage to increase the coupling efficiency by a factor of 129 compared with the situation without antennas. © 2009 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.optik.1optik.excita

Executing Algorithms for Optimization and Quantum Phase Recognition on a Superconducting Quantum Processor - Eichler, Christopher (Seminar hosted by Michael Hartmann, 2021)
Keywords: wwwqudev

Exotic looped trajectories of photons in three-slit interference - Magaña-Loaiza, Omar S; De Leon, Israel; Mirhosseini, Mohammad; Fickler, Robert; Safari, Akbar; Mick, Uwe; McIntryre, Brian; Banzer, Peter; Rodenburg, Brandon; Leuchs, Gerd; Boyd, Robert W. (Nature Communications, 2016)
The validity of the superposition principle and of Born's rule are well-accepted tenants of quantum mechanics. Surprisingly, it has been predicted that the intensity pattern formed in a three-slit experiment is seemingly in contradiction with the most conventional form of the superposition principle when exotic looped trajectories are taken into account. However, the probability of observing such paths is typically very small, thus rendering them extremely difficult to measure. Here we confirm the validity of Born's rule and present the first experimental observation of exotic trajectories as additional paths for the light by directly measuring their contribution to the formation of optical interference fringes. We accomplish this by enhancing the electromagnetic near-fields in the vicinity of the slits through the excitation of surface plasmons. This process increases the probability of occurrence of these exotic trajectories, demonstrating that they are related to the near-field component of the photon's wavefunction.

Expansion of the dynamic range of a Shack-Hartmann sensor by using astigmatic microlenses - Lindlein, Norbert; Pfund, Johannes; Schwider, Johannes (Optical Engineering, 2000)
The dynamic range of a Shack-Hartmann sensor is normally limited by the fact that the foci can leave their subapertures and so a definite attachment of the foci to their subapertures is difficult. One method for solving this problem is to give the focal spots a kind of label to identify them even if they leave their subaperture. We describe how the dynamic range of a Shack-Hartmann sensor can be expanded by using lenses with well-defined astigmatism. We also derive a relation between the spot displacements and the partial derivatives of the wavefront for large wavefront slopes.
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.expans

Experimental Comparison of All-Optical Phase-Preserving Amplitude Regeneration Techniques - Endres, D.; Stephan, C.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (12th International Conf. on Digital Object Identifier (ICTON), Munich, June, 2010)
lhft_intern.bib::Endres10

Experimental continuous-variable cloning of partial quantum information - Leuchs, Gerd; et al. (Physical Review A, 2008)
The fidelity of a quantum transformation is strongly linked with the prior partial information of the state to be transformed. We illustrate this interesting point by proposing and demonstrating the superior cloning of coherent states with prior partial information. More specifically, we propose two simple transformations that under the Gaussian assumption optimally clone symmetric Gaussian distributions of coherent states as well as coherent states with known phases. Furthermore, we implement for the first time near-optimal state-dependent cloning schemes relying on simple linear optics and feedforward. © 2008 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2008.nat.dphy.optik.1optik.experi_3

Experimental cross-polarization detection of coupling far-field light to highly confined plasmonic gap modes via nanoantennas - Wen, J.; Banzer, Peter; Kriesch, Arian; Ploss, Daniel; Schmauß, Bernhard; Peschel, Ulf (Applied Physics Letters, 2011)
We experimentally demonstrate the coupling of far-field light to highly confined plasmonic gap modes via connected nanoantennas. The excitation of plasmonic gap modes is shown to depend on the polarization, position, and wavelength of the incident beam. Far-field measurements performed in crossed polarization allow for the detection of extremely weak signals re-emitted from gap waveguides and can increase the signal-to-noise ratio dramatically.
lhft_intern.bib::Wen11

Experimental cryptography using continuous polarization states - Leuchs, Gerd; et al. (Quantum Communications and Cryptograph, 2006)
UnivIS-Import:2015-04-20:Pub.2006.nat.dphy.optik.1optik.experi_8

Experimental Demonstration of Coherent State Estimation with Minimal Disturbance - Leuchs, Gerd; et al. (Physical Review Letters, 2006)
We investigate the optimal trade-off between information gained about an unknown coherent state and the state disturbance caused by the measurement process. We propose several optical schemes that can enable this task, and we implement one of them, a scheme that relies on only linear optics and homodyne detection. Experimentally we reach near optimal performance, limited only by detection inefficiencies. In addition, we show that such a scheme can be used to enhance the transmission fidelity of a class of noisy channels. © 2006 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2006.nat.dphy.optik.1optik.experi

Experimental demonstration of continuous variable cloning with phase-conjugate inputs - Leuchs, Gerd; et al. (Physical Review Letters, 2007)
We report the first experimental demonstration of continuous variable cloning of phase-conjugate coherent states as proposed by Cerf and Iblisdir. In contrast to this proposal, the cloning transformation is accomplished using only linear optical components, homodyne detection, and feedforward. As a result of combining phase conjugation with a joint measurement strategy, superior cloning is demonstrated with cloning fidelities reaching 89%. © 2007 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2007.nat.dphy.optik.1optik.experi_7

Experimental Demonstration of Continuous Variable Entanglement Distillation - Dong, Ruifang; Lassen, Mikael Ostergaard; Marquardt, Christoph; Filip, Radim; Andersen, Ulrik Lund; Leuchs, Gerd (Quantum Electronics and Laser Science Conference 2008, 2008)
We experimentally demonstrate distillation of continuous variable entanglement through an attenuating quantum channel. Through a simple protocol based entirely on linear optics and homodyne detection we probabilistically filter out a highly entangled state from a less non-entangled mixed state.<br

Experimental Demonstration of Continuous Variable Quantum Erasing - Leuchs, Gerd; et al. (Physical Review Letters, 2004)
The concept of continuous variable quantum erasing was analyzed by using light beams. The quantum nondemolition (QND) coupling was accomplished by using a beam splitter coupled to squeezed light. It was observed that the phase quadrature information of the single state could be recovered by erasing the amplitude quadrature information. It was also observed that the measured values of open diamonds increased when the degree of input squeezing was reduced.
UnivIS-Import:2015-03-09:Pub.2004.nat.dphy.optik.1optik.experi

Experimental demonstration of linear and spinning Janus dipoles for polarisation- and wavelength-selective near-field coupling - Picardi, Michela F.; Neugebauer, Martin; Eismann, Joerg S.; Leuchs, Gerd; Banzer, Peter; Rodriguez-Fortuno, Francisco J.; Zayats, Anatoly V. (Light: Science & Applications, 2019)
The electromagnetic field scattered by nano-objects contains a broad range of wavevectors and can be efficiently coupled to waveguided modes. The dominant contribution to scattering from subwavelength dielectric and plasmonic nanoparticles is determined by electric and magnetic dipolar responses. Here, we experimentally demonstrate spectral and phase selective excitation of Janus dipoles, sources with electric and magnetic dipoles oscillating out of phase, in order to control near-field interference and directional coupling to waveguides. We show that by controlling the polarisation state of the dipolar excitations and the excitation wavelength to adjust their relative contributions, directionality and coupling strength can be fully tuned. Furthermore, we introduce a novel spinning Janus dipole featuring cylindrical symmetry in the near and far field, which results in either omnidirectional coupling or noncoupling. Controlling the propagation of guided light waves via fast and robust near-field interference between polarisation components of a source is required in many applications in nanophotonics and quantum optics.
CRIS-Team Scopus Importer:2019-06-21

Experimental demonstration of macroscopic quantum coherence in Gaussian states - Marquardt, Christoph; Andersen, Ulrik L.; Leuchs, Gerd; Takeno, Yuishi; Yukawa, Mitsuyoshi; Yonezawa, Hidehiro; Furusawa, Akira (Physical Review A, 2007)
We witness experimentally the presence of macroscopic coherence in Gaussian quantum states using a recently proposed criterion. The macroscopic coherence stems from interference between macroscopically distinct states in phase space, and we prove experimentally that a coherent state contains these features with a distance in phase space of 0.51±0.02 shot noise units. This is surprising because coherent states are generally considered being at the border between classical and quantum states, not yet displaying any nonclassical effect. For squeezed and entangled states the effect may be larger but depends critically on the state purity. © 2007 The American Physical Societ
UnivIS-Import:2015-03-09:Pub.2007.nat.dphy.optik.1optik.experi_8

Experimental demonstration of the geometric spin hall effect of light in highly focused vector beams - Neugebauer, Martin; Banzer, Peter; Bauer, Thomas; Lindlein, Norbert; Aiello, Andrea; Marquardt, Christoph; Korger, Jan; Leuchs, Gerd (Quantum Electronics and Laser Science Conference, QELS 2012, 2012)
We demonstrate the geometric spin Hall effect of light by focusing a specially polarization tailored beam of light, resulting in the generation of purely transverse angular momentum in the focal plane. © 2012 OS

Experimental Distillation of Squeezed States - Heersink, Joel; Marquardt, Christoph; Filip, Radim; Dong, Ruifang; Chekhova, Maria V.; Lorenz, S.; Leuchs, Gerd; Andersen, Ulrik Lund (QThL3 Quantum Electronics and Laser Science Conference (CLEO:FS), 2006)
We report on the first experimental distillation of an intense squeezed state from a non-Gaussian mixture of polarization squeezed states. Conditioning the signal on a tap measurement, we observe probabilistic recovery of the squeezing.<br

Experimental entanglement distillation of mesoscopic quantum states - Dong, Ruifang; Lassen, Mikael; Heersink, Joel; Marquardt, Christoph; Filip, Radim; Leuchs, Gerd; Andersen, L. Ulrik (Nature Physics, 2008)
The distribution of entangled states between distant parties in an optical network is crucial for the successful implementation of various quantum communication protocols such as quantum cryptography, teleportation and dense coding. However, owing to the unavoidable loss in any real optical channel, the distribution of loss-intolerant entangled states is inevitably afflicted by decoherence, which causes a degradation of the transmitted entanglement. To combat the decoherence, entanglement distillation, a process of extracting a small set of highly entangled states from a large set of less entangled states, can be used. Here we report on the distillation of deterministically prepared light pulses entangled in continuous variables that have undergone non-Gaussian noise. The entangled light pulses are sent through a lossy channel, where the transmission is varying in time similarly to light propagation in the atmosphere. By using linear optical components and global classical communication, the entanglement is probabilisticallyincreased. © 2008 Macmillan Publishers Limited. All rights reserve
UnivIS-Import:2015-03-09:Pub.2008.nat.dphy.optik.1optik.experi

Experimental evidence for Raman-induced limits to efficient squeezing in optical fibers - Leuchs, Gerd; et al. (Optics Letters, 2008)
We report new experiments on polarization squeezing using ultrashort photonic pulses in a single pass of a birefringent fiber. We measure what is to our knowledge a record squeezing of -6.8±0.3 dB in optical fibers, which when corrected for linear losses is -10.4±0.8 dB. The measured polarization squeezing as a function of optical pulse energy, which spans a wide range from 3.5-178.8 pJ, shows a very good agreement with the quantum simulations, and for the first time we see the proof experimentally that Raman effects limit and reduce squeezing at high pulse energy. © 2008 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2008.nat.dphy.optik.1optik.experi_9

Experimental generation of amplitude squeezed vector beams - Chille, Vanessa; Berg-Johansen, Stefan; Semmler, Marion; Banzer, Peter; Aiello, Andrea; Leuchs, Gerd; Marquardt, Christoph (Optics Express, 2016)
We present an experimental method for the generation of amplitude squeezed high-order vector beams. The light is modified twice by a spatial light modulator such that the vector beam is created by means of a collinear interferometric technique. A major advantage of this approach is that it avoids systematic losses, which are detrimental as they cause decoherence in continuous-variable quantum systems. The utilisation of a spatial light modulator (SLM) gives the flexibility to switch between arbitrary mode orders. The conversion efficiency with our setup is only limited by the efficiency of the SLM. We show the experimental generation of Laguerre-Gauss (LG) modes with radial indices 0 or 1 and azimuthal indices up to 3 with complex polarization structures and a quantum noise reduction up to -0.9dB±0.1dB. The corresponding polarization structures are studied in detail by measuring the spatial distribution of the Stokes parameters.
CRIS-Team Scopus Importer:2022-06-05

Experimental Investigation of a Modified NOLM for Phase-Encoded Signal Regeneration - Cvecek, Kristian; Onishchukov, Georgy; Sponsel, Klaus; Striegler, Arne; Schmauß, Bernhard (IEEE Photonics Technology Letters, 2006)
We experimentally investigate the amplitude and phase transfer characteristics of a modified nonlinear optical loop mirror (NOLM) with a directional attenuator (DA-NOLM) optimized for differential phase-shift keying signal regeneration. The results show that the phase relation is preserved in the setup and thus the DA-NOLM is suitable for amplitude regeneration of phase-shift-keyed signals. © 2006 IEEE.
UnivIS-Import:2015-04-14:Pub.2006.tech.IE.LEH.experi
Keywords: 2R regeneration; All-optical regeneration; Differential phase-shift keying (DPSK); Nonlinear optical loop mirror (NOLM)

Experimental measurement of the Berry curvature from anomalous transport - Wimmer, Martin; Price, Hannah M.; Carusotto, Iacopo; Peschel, Ulf (Nature Physics, 2017)
The geometric properties of energy bands underlie fascinating phenomena in many systems, including solid-state, ultracold gases and photonics. The local geometric characteristics such as the Berry curvature can be related to global topological invariants such as those classifying the quantum Hall states or topological insulators. Regardless of the band topology, however, any non-zero Berry curvature can have important consequences, such as in the semi-classical evolution of a coherent wavepacket. Here, we experimentally demonstrate that the wavepacket dynamics can be used to directly map out the Berry curvature. To this end, we use optical pulses in two coupled fibre loops to study the discrete time evolution of a wavepacket in a one-dimensional geometric 'charge' pump, where the Berry curvature leads to an anomalous displacement of the wavepacket. This is both the first direct observation of Berry curvature effects in an optical system, and a proof-of-principle demonstration that wavepacket dynamics can serve as a high-resolution tool for mapping out geometric properties.
CRIS-Team Scopus Importer:2023-04-20

Experimental Optical Simulator of Reconfigurable and Complex Quantum Environment - Renault, P.; Nokkala, J.; Roeland, G.; Joly, Nicolas; Zambrini, R.; Maniscalco, S.; Piilo, J.; Treps, N.; Parigi, V. (PRX Quantum, 2023)
No quantum system can be considered totally isolated from its environment. In most cases the interaction between the system of interest and the external degrees of freedom deeply changes its dynamics, as described by open quantum system theory. Nevertheless engineered environment can be turned into beneficial effects for some quantum information tasks. Here we demonstrate an optical simulator of a quantum system coupled to an arbitrary and reconfigurable environment built as a complex network of quantum interacting systems. We experimentally retrieve typical features of open quantum system dynamics like the spectral density and quantum non-Markovianity, by exploiting squeezing and entanglement correlation of a continuous-variable optical platform. This opens the way to the experimental tests of open quantum systems in reconfigurable environments that are relevant in, among others, quantum information, quantum thermodynamics, quantum transport, and quantum synchronization.
CRIS-Team Scopus Importer:2023-11-10

Experimental Polarization Squeezing and Continuous Variable Entanglement via the Optical Kerr Effect - Leuchs, Gerd; et al. (Quantum Information with continuous variables of atoms and light, 2007)
UnivIS-Import:2015-04-20:Pub.2007.nat.dphy.optik.1optik.experi_9

Experimental Quantum Cloning with Continuous Variables - Leuchs, Gerd; Andersen, Ulrik Lund; Lütkenhaus, Norbert; et al. (Quantum Information with continuous variables of atoms and light, 2007)
UnivIS-Import:2015-04-20:Pub.2007.nat.dphy.optik.1optik.experi

Experimental quantum purification of coherent states - Leuchs, Gerd; et al. (Physical Review A, 2005)
UnivIS-Import:2015-03-09:Pub.2005.nat.dphy.optik.1optik.experi

Experimental realization of an absolute single-photon source based on a single nitrogen vacancy center in a nanodiamond - Rodiek, Beatrice; Lopez, Marco; Hofer, Helmuth; Porrovecchio, Geiland; Smid, Marek; Chu, Xiao-Liu; Götzinger, Stephan; Sandoghdar, Vahid; Lindner, Sarah; Becher, Christoph; Kuck, Stefan (Optica, 2017)
We report on the experimental realization of an absolute single-photon source based on a single nitrogen vacancy (NV) center in a nanodiamond at room temperature and on the calculation of its absolute spectral photon flux from experimental data. The single-photon source was calibrated with respect to its photon flux and its spectral photon rate density. The photon flux was measured with a low-noise silicon photodiode traceable to the primary standard for optical flux, taking into account the absolute spectral power distribution using a calibrated spectroradiometer. The optical radiant flux is adjustable from 55 fW, which is almost the lowest detection limit for the silicon photodiode, and 75 fW, which is the saturation power of the NV center. These fluxes correspond to total photon flux rates between 190,000 photons per second and 260,000 photons per second, respectively. The single-photon emission purity is indicated by a g(2)(0) value, which is between 0.10 and 0.23, depending on the excitation power. To our knowledge, this is the first single-photon source absolutely calibrated with respect to its absolute optical radiant flux and spectral power distribution, traceable to the corresponding national standards via an unbroken traceability chain. The prospects for its application, e.g., for the detection efficiency calibration of single-photon detectors as well as for use as a standard photon source in the low photon flux regime, are promising.
CRIS-Team Scopus Importer:2023-03-27
Keywords: Metrology; Photon statistics; Radiometry; Sources

Experimental reconstruction of spatial Schmidt modes for a wide-field SU(1,1) interferometer - Frascella, Gaetano; Zakharov, Roman V.; Tikhonova, Olga V.; Chekhova, Maria (Laser Physics, 2019)
We study the spatial mode content at the output of a wide-field SU(1,1) interferometer, i.e. a nonlinear interferometer comprising two coherently-pumped spatially-multimode optical parametric amplifiers placed in sequence with a focusing element in between. This device is expected to provide a phase sensitivity below the shot-noise limit for multiple modes over a broad angular range. To reconstruct the spatial modes and their weights, we implement a simple method based on the acquisition of only intensity distributions. The eigenmode decomposition of the field is obtained through the measurement of the covariance of intensities at different spatial points. We investigate both the radial and azimuthal (orbital angular momentum) modes and show that their total number is large enough to enable applications of the interferometer in spatially-resolved phase measurements.
CRIS-Team Scopus Importer:2020-02-21
Keywords: Orbital angular momentum; Parametric down-conversion; Schmidt modes; SU(1; 1) interferometer

Experimental results for expanding the dynamic range of a Shack-Hartmann sensor using astigmatic microlenses - Lindlein, Norbert; et al. (Optical Engineering, 2002)
A conventional Shack-Hartmann wavefront sensor cannot be used for the measurement of wavefronts with steep slopes if the spots leave their respective subapertures. In an earlier paper [N. Lindlein, J. Pfund, and J. Schwider, "Expansion of the dynamic range of a Shack-Hartmann sensor by using astigmatic microlenses," Opt. Eng. 39(8), 2220-2225 (2000)], we described a method to expand the dynamic range of a Shack-Hartmann wavefront sensor by marking the spots using astigmatic microlenses. We present experimental results for this method and describe how this special sensor can be interpreted as a combination of several Shack-Hartmann sensors with enlarged subapertures.
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.experi
Keywords: Dynamic range expansion; Microlenses; Shack-Hartmann sensor; Wavefront sensor

Experimental results of the simultaneous measurement of spatially varying phase and polarization. - Rothau, Sergej; Kellermann, Christine; Lindlein, Norbert (116. Annual Meeting of the DGaO, 2015)

Experimental results of the simultaneous measurement of spatially varying phase and polarization - Rothau, Sergej; Kellermann, Christine; Lindlein, Norbert (2015)

Experimental Tomographic State Reconstruction of Itinerant Microwave Photons - Eichler, Christopher; et al. (QSIT lunch seminar, 2010)
A wide range of experiments studying microwave photons localized in superconducting cavities have made important contributions to our understanding of the quantum properties of radiation. Propagating microwave photons, however, have so far been studied much less intensely. Here we present measurements in which we reconstruct the Wigner function of itinerant single photon Fock states and their superposition with the vacuum using linear amplifiers and quadrature amplitude detectors. We have developed efficient methods to separate the detected single photon signal from the noise added by the amplifier by analyzing the moments of the measured amplitude distribution up to 4th order. This work is expected to enable studies of propagating microwaves in the context of linear quantum optics. Combining single photon sources with beamsplitter and squeezing devices, efficient photon state measurements could allow for future linear optics quantum computation with microwaves photons.
Keywords: wwwqudev

Experimental verification of high spectral entanglement for pulsed waveguided spontaneous parametric down-conversion - Leuchs, Gerd; et al. (Physical Review A, 2009)
We study the spectral properties of spontaneous parametric down-conversion (SPDC) in a periodically poled waveguided structure of potassium-titanyl- phosphate (KTP) crystal pumped by ultrashort pulses. Our theoretical analysis reveals a strongly entangled and asymmetric structure of the two-photon spectral amplitude for type-II SPDC. We confirm these predictions experimentally by measuring single-photon spectra, on one hand, and the dependence of Hong-Ou-Mandel interference visibility on the width of spectral filtering, on the other hand. © 2009 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.optik.1optik.experi

Experiment towards continuous-variable entanglement swapping: Highly correlated four-partite quantum state - Glöckl, Oliver; Lorenz, Stefan; Marquardt, Christoph; Heersink, Joel; Brownnutt, Michael; Silberhorn, Christine; Pan, Quing; van Loock, Peter; Korolkova, Natalia; Leuchs, Gerd (Physical Review A - Atomic, Molecular, and Optical Physics, 2003)
We present a protocol for performing entanglement swapping with intense pulsed beams. In a first step, the generation of amplitude correlations between two systems that have never interacted directly is demonstrated. This is verified in direct detection with electronic modulation of the detected photocurrents. The measured correlations are better than expected from a classical reconstruction scheme. In an entanglement swapping process, a four-partite entangled state is generated. We prove experimentally that the amplitudes of the four optical modes are quantum correlated 3 dB below shot noise, which is consistent with the presence of genuine four-party entanglement.<br

Exploring quantum microwave radiation emitted from superconducting electronic circuits - Eichler, Christopher (2013)
Superconducting electronic circuits have turned into one of the prime physical systems to investigate quantum optical and atomic physics phenomena in engineered solid state devices. While the on-demand generation and the processing of quantum states on a chip are now routinely achieved with high fidelity, it remains challenging to detect propagating microwave photons with equally high efficiency. This is mainly due to the absence of efficient photon counters in this frequency range. In my presentation, I explain how we employ low-noise linear amplifiers instead of photon counters for measuring microwave field correlations at the quantum level. For this purpose we have developed efficient data acquisition, processing and analysis techniques to separate the quantum signal of interest from the noise added by the amplifiers [1]. In our experiments we have successfully generated and characterized various types of interesting quantum fields, ranging from on-demand single photons [2], over squeezed radiation [3], to spatially entangled fields [4]. Recently, we have also developed our own parametric amplifiers to perform nearly quantum limited measurements of microwave radiation [3,6]. These enabled us to observe entanglement between a quantum two-level system and microwave photons propagating freely through a transmission line [5]. The possibility to accurately synthesize, guide and characterize non-classical microwave fields bears great potential to be used in radiation based quantum simulation and quantum network architectures and for probing other systems with yet unrivaled sensitivity. References: [1] C. Eichler et al., PRA 86, 032106–13 (2012), [2] C. Eichler et al., PRL. 106, 220503 (2011), [3] C. Eichler et al., PRL 107, 113601 (2011), [4] C. Lang et al. Nat. Phys., in print (2013), [5] C. Eichler et al., PRL. 109, 240501 (2012), [6] C. Eichler and Wallraff, A., arXiv:1305.6583
Keywords: wwwqudev

Exploring Quantum Microwave Radiation Using Linear Detectors - Eichler, Christopher (Workshop on Quantum Radar, 2014)
Keywords: wwwqudev

Extraordinary low transmission effects for ultra-thin patterned metal films - Reibold, David; Shao, F.; Erdmann, Andreas; Peschel, Ulf (Optics Express, 2009)
Thin metal films show a residual transmission for light in the visible and UV spectral range. This transmission can be strongly reduced by an appropriate sub-wavelength patterning of the metal film. Our investigation is focused on metal films with a thickness much below 100nm, where the transmission response is dominated by the individual posts acting like antennas and cannot be attributed to the excitation of surface plasmons. The almost complete suppression of transmission for ultra-thin metal films depends mainly on the absorber width, but not on the pitch of the pattern. The effect is robust with respect to imperfections of the geometry or larger features imprinted into the sub-wavelength pattern. © 2008 Optical Society of America.
UnivIS-Import:2017-07-10:Pub.2009.tech.IE.LEB.extrao

Extraordinary transmission through a single coaxial aperture in a thin metal film - Banzer, Peter; Kindler, Jochen; Quabis, Susanne; Peschel, Ulf; Leuchs, Gerd (Optics Express, 2010)
We investigate experimentally the transmission properties of single sub-wavelength coaxial apertures in thin metal films (t = 110 nm). Enhanced transmission through a single sub-wavelength coaxial aperture illuminated with a strongly focused radially polarized light beam is reported. In our experiments we achieved up to four times enhanced transmission through a single coaxial aperture as compared to a (hollow) circular aperture with the same outer diameter.We attribute this enhancement of transmission to the excitation of a TEM-mode for illumination with radially polarized light inside the single coaxial aperture. A strong polarization contrast is observed between the transmission for radially and azimuthally polarized illumination. Furthermore, the observed transmission through a single coaxial aperture can be strongly reduced if surface plasmons are excited. The experimental results are in good agreement with finite difference time domain (FDTD) simulations.
EAM Import::2019-03-14

Extreme Concentration and Nanoscale Interaction of Light - Leuchs, Gerd; Andrianov, Alexey V.; Anashkina, Elena A.; Manshina, Alina A.; Banzer, Peter; Sondermann, Markus (ACS Photonics, 2022)
Concentrating light strongly calls for appropriate polarization patterns of the focused light beam and for up to a full 4πsolid angle geometry. Focusing on the extreme requires efficient coupling to nanostructures of one kind or another via cylindrical vector beams having such patterns, the details of which depend on the geometry and property of the respective nanostructure. Cylindrical vector beams can not only be used to study a nanostructure, but also vice versa. Closely related is the discussion of topics such as the ultimate diffraction limit, a resonant field enhancement near nanoscopic absorbers, as well as speculations about nonresonant field enhancement, which, if it exists, might be relevant to pair production in vacuum. These cases do require further rigorous simulations and more decisive experiments. While there is a wide diversity of scenarios, there are also conceptually very different models offering helpful intuitive pictures despite this diversity.
Created from Fastlane, Scopus look-up
Keywords: field enhancement; focusing; light-matter interactions; nonlinear optics; quantum optics

Extreme Events through Prevailing Backscattering and Their Suppression by a Focusing Nonlinearity - Schultheiß, Vincent; Wimmer, Martin; Malzer, Stefan; Peschel, Ulf (Physical Review X, 2018)
We investigate linear and nonlinear light propagation in weakly perturbed AlGaAs slab waveguides whose fabrication induced local defects give rise to random multiple scattering. The statistical evaluation of the intensity distribution at the rear facet reveals an abundance of high-amplitude events in the linear regime, contradicting the predictions of the central limit theorem by far. In this article we propose weak successive backscattering to be a generator of high-amplitude events, while a focusing nonlinearity of the Kerr type counterintuitively diminishes them, thus effectively randomizing the intensity distribution. We support our experimental findings with numerical simulations based on the stray matrix approach introduced by Edrei et al. [Phys. Rev. Lett. 62, 2120 (1989)]. This novel proposed mechanism for the formation of extreme events in the context of linear wave dynamics represents the first encounter of the phenomenon in the limit of weak scattering.
CRIS-Team WoS Importer:2019-02-20

Extreme thermodynamics in nanolitre volumes through stimulated Brillouin–Mandelstam scattering - Geilen, Andreas; Popp, Alexandra; Das, Debayan; Junaid, Saher; Poulton, Christopher G.; Chemnitz, Mario; Marquardt, Christoph; Schmidt, Markus A.; Stiller, Birgit (Nature Physics, 2023)
Examining the physical properties of materials—particularly of toxic liquids—under a wide range of thermodynamic states is a challenging problem due to the extreme conditions the material has to experience. Such temperature and pressure regimes, which result in a change in the refractive index and sound velocity, can be accessed by optoacoustic interactions such as Brillouin–Mandelstam scattering. Here we demonstrate the Brillouin–Mandelstam measurements of nanolitre volumes of liquids in extreme thermodynamic regimes. This is enabled by a fully sealed liquid-core optical fibre containing carbon disulfide. Within this waveguide, which exhibits tight optoacoustic confinement and a high Brillouin gain, we are able to conduct spatially resolved measurements of the local Brillouin response, giving us access to a resolved image of the temperature and pressure values along the liquid channel. We measure the material properties of the liquid core at very large positive pressures (above 1,000 bar) and substantial negative pressures (below –300 bar), as well as explore the isobaric and isochoric regimes. The extensive thermodynamic control allows the tunability of the Brillouin frequency shift of more than 40% using only minute volumes of liquid.
CRIS-Team Scopus Importer:2023-10-06

Fabrication and characterization of plasmonic nanocone antennas for strong spontaneous emission enhancement - Hoffmann, Björn; Vassant, Simon; Chen, Xue-Wen; Götzinger, Stephan; Sandoghdar, Vahid; Christiansen, Silke (Nanotechnology, 2015)
Plasmonic antennas are attractive nanostructures for a large variety of studies ranging from fundamental aspects of light-matter interactions at the nanoscale to industry-relevant applications such as ultrasensitive sensing, enhanced absorption in solar cells or solar fuel generation. A particularly interesting feature of these antennas is that they can enhance the fluorescence properties of emitters. Theoretical calculations have shown that nanocone antennas provide ideal results, but a high degree of manufacturing precision and control is needed to reach optimal performance. In this study, we report on the fabrication of nanocones with base diameters and heights in the range of 100 nm with variable aspect ratios using focused ion beam milling of sputtered nano-crystalline gold layers. The controlled fabrication process allows us to obtain cones with tailored plasmon resonances. The measured plasmon spectra show very good agreement with finite-difference time-domain calculations. Theoretical investigations predict that these nanocones can enhance the spontaneous emission rate of a quantum emitter by several hundred times while keeping its quantum efficiency above 60%.
Keywords: focused ion beam; nanocone antenna; plasmon spectroscopy; plasmonics; radiative rate enhancement

Fabrication and characterization of tapered single-ring hollow-core photonic crystal fibre - Pennetta, Riccardo; Enders, Michael T.; Frosz, Michael H.; Tani, Francesco; Russell, Philip St. John (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Thermal tapering of step-index and photonic crystal fibres (PCF) has recently emerged as an effective tool for controlling nonlinear optical effects through offering axially varying dispersion and high effective nonlinearity [1,2]. At the same time, rapid developments in hollow-core PCF have opened up new possibilities for gas-based nonlinear optics. In particular, single-ring PCF (SR-PCF), consisting of a circular ring of thin-walled capillaries surrounding a central hollow core, can offer low-loss, easily predictable windows of transparency, effectively single-mode guidance and is relatively simple to fabricate [3]. Here we show, for the first time to our knowledge, the fabrication and non-invasive characterization of tapered SR-PCF.
CRIS-Team Scopus Importer:2019-11-15

Fabrication and optical characterisation of InGaN/GaN nanorods - Dai, Xi; Wen, Xiaoming; Latzel, Michael; Heilmann, Martin; Appelt, Christian; Feng, Yu; Yang, Jianfeng; Chen, Weijian; Huang, Shujuan; Shrestha, Santosh; Christiansen, Silke; Conibeer, Gavin (Proceedings of SPIE - The International Society for Optical Engineering, 2015)
We report the fabrication of densely packed InGaN/GaN nanorods with high hexagonal periodicity. Nanosphere lithography and reactive ion etching were adopted to fabricate the nanorods from planar multiple quantum wells (MQWs). Compared to the planar MQWs, the nanorods exhibit significant luminescence enhancement. This is mostly attributed to the increased radiative recombination and light extraction efficiency. Both photoluminescence and Raman measurements confirmed in-plane strain relaxation in the MQWs after nanofabrication. A reduction in strain-induced quantum confined Stark effect in the nanorods increased radiative recombination. This work is most crucial to the understanding of optical properties with respect to the carrier transport and recombination in InGaN/GaN nanorods.
CRIS-Team Scopus Importer:2023-03-07
Keywords: cathodoluminescence; Langmuir-Blodgett approach; Nanorods; photoluminescence; Raman; reactive ion etching

Fabrication of genuine single-quantum-dot light-emitting diodes - Schmidt, Ralf; Scholz, Uwe; Vitzthum, Markus; Fix, Richard; Metzner, Claus; Kailuweit, Peter; Reuter, Dirk; Wieck, Andreas; Hübner, M.C.; Stufler, Stefan; Zrenner, Arthur; Malzer, Stefan; et al. (Applied Physics Letters, 2006)
We present a simple approach for the fabrication of genuine single quantum-dot light-emitting diodes. A submicron wide bottom contact stripe is formed by focused ion beam implantation doping into a GaAs buffer layer. Successive overgrowth with a thin intrinsic layer incorporating self-assembled InAs quantum dots, followed by a top contact layer of complementary doping type and standard photolithographic processing, allows for electrical cross sections in the sub- μ m range. In devices with sufficiently low dot densities, only one single dot is expected to be electrically addressed. Both the observed current versus voltage characteristics and the evolution of the electroluminescence spectra as a function of applied voltage clearly demonstrate that this goal has been achieved. © 2006 American Institute of Physics.

Fading channel estimation for free-space continuous-variable secure quantum communication - Ruppert, Laszlo; Peuntinger, Christian; Heim, Bettina; Günthner, Kevin; Usenko, Vladyslav C.; Elser, Dominique Alexander; Leuchs, Gerd; Filip, Radim; Marquardt, Christoph (New Journal of Physics, 2019)
We investigate estimation of fluctuating channels and its effect on security of continuous-variable quantum key distribution. We propose a novel estimation scheme which is based on the clusterization of the estimated transmittance data. We show that uncertainty about whether the transmittance is fixed or not results in a lower key rate. However, if the total number of measurements is large, one can obtain using our method a key rate similar to the non-fluctuating channel even for highly fluctuating channels. We also verify our theoretical assumptions using experimental data from an atmospheric quantum channel. Our method is therefore promising for secure quantum communication over strongly fluctuating turbulent atmospheric channels.
CRIS-Team WoS Importer:2020-03-06

Far field calculation of distorted Gaussian beams - Pflaum, Christoph; Rall, Phillip Lino; Lindlein, Norbert (Journal of the Optical Society of America A-Optics Image Science and Vision, 2022)
Far field calculations of beams, such as laser beams, are often applied in optical engineering. Current beam propagation methods fail in certain range parameters due to high storage requirements of the algorithms. This paper presents a new beam propagation method for far field calculations of distorted Gaussian beams in a homogeneous medium including optical elements, such as lenses. The method works even in the case of a large distance from the observation plane to the beam waist and can be applied to larger divergence angles. This new simulation technique factors out the phase of the Gaussian TEM00 beam and solves the resulting partial differential equation by suitable finite difference or finite element discretization methods.<br

Fast 3d - Camera for Industrial and Medical Applications - Häusler, Gerd; et al. (Proc. of ODIMAP II, 1999)
UnivIS-Import:2015-04-16:Pub.1999.nat.dphy.optik.1optik.fast3d

Feasibility of free space quantum key distribution with coherent polarization states - Heim, Bettina; Leuchs, Gerd; et al. (New Journal of Physics, 2009)
We demonstrate for the first time the feasibility of free space quantum key distribution with continuous variables under real atmospheric conditions. More specifically, we transmit coherent polarization states over a 100m free space channel on the roof of our institute's building. In our scheme, signal and local oscillator (LO) are combined in a single spatial mode, which auto-compensates atmospheric fluctuations and results in an excellent interference. Furthermore, the LO acts as a spatial and spectral filter, thus allowing unrestrained daylight operation. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
UnivIS-Import:2015-04-14:Pub.2009.nat.dphy.optik.1optik.feasib

Feasibility of quantum key distribution with macroscopically bright coherent light - Kovalenko, Olena; Spasibko, Kirill; Chekhova, Maria; Usenko, Vladyslav C.; Filip, Radim (Optics Express, 2019)
We address feasibility of continuous-variable quantum key distribution using bright multimode coherent states of light and homodyne detection. We experimentally verify the possibility to properly select signal modes by matching them with the local oscillator and this way to decrease the quadrature noise concerned with unmatched bright modes. We apply the results to theoretically predict the performance of continuous-variable quantum key distribution scheme using multimode coherent states in scenarios where modulation is applied either to all the modes or only to the matched ones, and confirm that the protocol is feasible at high overall brightness. Our results open the pathway towards full-scale implementation of quantum key distribution using bright light, thus bringing quantum communication closer to classical optics.
CRIS-Team Scopus Importer:2019-12-24

Feasibility of squeezing detection over satellite links - Muller, Christian R.; Seshadreesan, Kaushik P.; Leuchs, Gerd; Marquardt, Christoph (2017 IEEE International Conference on Space Optical Systems and Applications, ICSOS 2017, 2018)
Quantum squeezing is the nonlinear quantum mechanical effect by which the Heisenberg uncertainty in one observable can be reduced below the shot noise level at the expense of increased uncertainty in its conjugate observable. We study the detection of optical quadrature squeezing via homodyne detection in satellite links. The propagation of the quantum states over large distances and through a varying gravitational potential offers the possibility to test the fundamental laws of physics at the interface of quantum mechanics and general relativity. We model the task as a binary hypothesis testing problem where the null hypothesis corresponds to the vacuum state and the alternative hypothesis corresponds to the squeezed state. Using the Chernoff bound, we derive the number of individual measurements required to limit the average error probabilities to a given value.
CRIS-Team Scopus Importer:2022-06-05
Keywords: Continuous-variables; Homodyne detection; Optical satellite communication; Quadrature squeezing

Fiber-modes and fiber-anisotropy characterization using low-coherence interferometry - Ma, Y. Z.; Sych, Denis; Onishchukov, Georgy; Ramachandran, S.; Peschel, Ulf; Schmauß, Bernhard; Leuchs, Gerd (Applied Physics B-Lasers and Optics, 2009)
An optical low-coherence interferometry technique has been used to simultaneously resolve the mode profile and to measure the intermodal dispersion of guided modes of a few-mode fiber. Measurements are performed using short samples of fiber (about 50 cm). There is no need for a complex mode-conversion technique to reach a high interference visibility. Four LP mode groups of the few-mode fiber are resolved. Experimental results and numerical simulations show that the ellipticity of the fiber core leads to a distinct splitting of the degenerate high-order modes in group index. For the first time, to the best of our knowledge, it has been demonstrated that degenerate LP11 modes are much more sensitive to core shape variations than the fundamental modes and that intermodal dispersion of high-order degenerate modes can be used for characterizing the anisotropy of an optical waveguide.
UnivIS-Import:2015-04-14:Pub.2009.nat.dphy.optik.1optik.fiberm

Fiber optic based system for polarization sensitive spectroscopy of semiconductor quantum structures - Arora, Ashish; Karmakar, Biswajit; Sharma, Sayan; Schardt, Michael; Malzer, Stefan; Bansal, Bhavtosh; Döhler, Gottfried; Arora, Brij Mohan (Review of Scientific Instruments, 2010)
We describe an optical fiber based setup for performing polarization resolved magneto-optical spectroscopy measurements under low temperatures (∼4 K) and high magnetic fields (∼8 T). The measurements are performed in a windowless helium Dewar. Circularly polarized light is produced inside the Dewar by inserting the polarizing elements between the fiber end and the sample. Photoconductivity spectra of a GaAs/AlGaAs multiquantum-well sample have been measured over the photon energy range of 1.5-1.7 eV in left and right circularly polarized light under crossed magnetic and electric fields. It is shown that reversing the direction of magnetic field produces the same spectral changes as caused by changing the direction of circular polarization with the optical components. © 2010 American Institute of Physics.

Fiber Solitons—Quantum Interferometry and Entanglement - Leuchs, Gerd; Silberhorn, Christine; Glöckl, Oliver; Marquardt, Christoph; Korolkova, Natalia (Quantum Electronics and Laser Science Conference 2002, 2002)
The study of quantum properties of soliton pulses in fibers spans the full range from basic research to applications. New developments in high precision quantum interferometry and quantum communications will be reported as well as novel aspects of the range limit due to losses.<br

Fibre-based pressure-controlled sources for quantum optics - Joly, Nicolas; Hammer, Jakob; Chekhova, Maria (2021 Conference on Lasers and Electro-Optics, CLEO 2021 - Proceedings, 2021)
We present progress towards the generation of photon triplet states and realisation of a tunable source of entangled photons. In both cases, control of the phase-matching is achieved through gas-pressure tuning.
CRIS-Team Scopus Importer:2021-12-24

Fibre-optic photon-number squeezing in the normal group-velocity dispersion regime - Sizmann, Andreas; Fauster, Thomas; Leuchs, Gerd; et al. (Journal of Modern Optics, 1998)
The nonlinear optical Kerr effect, acting on optical pulses in fibres, creates spectral sidebands and noise correlations between these sidebands. The reduction of photon-number fluctuations of these pulses below the shot-noise limit by spectral filtering is well established in the anomalous dispersion regime which allows for soliton formation. Here it is demonstrated that a significant quantum-noise reduction with spectral filtering can also be reached for pulses in the normal dispersion regime. The filter function was optimized and the power dependence of the noise reduction was investigated. The best squeezing result is (1.2 ± 0.2) dB (corresponding to (2.6 ± 0.7) dB inferred for 100% detection efficiency).
UnivIS-Import:2015-03-05:Pub.1998.nat.dphy.optik.1optik.fibreo

Fibre Spectroscopy of Nanoscale Spontaneous Parametric Down-Conversion - Santiago Cruz, Tomás; Zhang Haizhong,; Anthur, Aravind P.; Krivitsky, Leonid; Chekhova, Maria (2020 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR), 2020)
CRIS-Team WoS Importer:2021-06-11

Flat-optics generation of broadband photon pairs with tunable polarization entanglement - Sultanov, Vitaliy; Santiago Cruz, Tomás; Chekhova, Maria (Optics Letters, 2022)
The concept of “flat optics” is quickly conquering different fields of photonics, but its implementation in quantum optics is still in its infancy. In particular, polarization entanglement, strongly required in quantum photonics, is so far not realized on “flat” platforms. Meanwhile, relaxed phase matching of “flat” nonlinear optical sources enables enormous freedom in tailoring their polarization properties. Here we use this freedom to generate photon pairs with tunable polarization entanglement via spontaneous parametric downconversion (SPDC) in a 400-nm GaP film. By changing the pump polarization, we tune the polarization state of photon pairs from maximally entangled to almost disentangled, which is impossible in a single bulk SPDC source. Polarization entanglement, together with the broadband frequency spectrum, results in an ultranarrow (12 fs) Hong–Ou–Mandel effect and promises extensions to hyperentanglement.
CRIS-Team Scopus Importer:2022-08-12

Flexible beam shaping system using fly's eye condenser - Lindlein, Norbert; Lano, Maik; Zimmermann, Maik; Bich, Andreas; Eisner, Martin; Harder, Irina; Voelkel, Reinhard; Weible, Ken (Applied Optics, 2010)
Normally, fly's eye condensers are used to homogenize light. However, in the case of fully coherent light, a fly's eye condenser, in connection with some simple optical elements, such as a diffractive axicon, a grating, and a telescope, can be used as a quite flexible beam shaping system, forming arrays of rings, parts of rings, or other structures with varying diameters. We present the principle, some simulation results, and some first experimental results. © 2010 Optical Society of America.

Fluorescence-based remote irradiation sensor in liquid-filled hollow-core photonic crystal fiber - Zeltner, Richard; Bykov, D. S.; Xie, S.; Euser, T. G.; Russell, Philip St. John (Applied Physics Letters, 2016)
We report an irradiation sensor based on a fluorescent ``flying particle'' that is optically trapped and propelled inside the core of a water-filled hollow-core photonic crystal fiber. When the moving particle passes through an irradiated region, its emitted fluorescence is captured by guided modes of the fiber core and so can be monitored using a filtered photodiode placed at the fiber end. The particle speed and position can be precisely monitored using in-fiber Doppler velocimetry, allowing the irradiation profile to be measured to a spatial resolution of 10 extgreekmm. The spectral response can be readily adjusted by appropriate choice of particle material. Using dye-doped polystyrene particles, we demonstrate detection of green (532 nm) and ultraviolet (340 nm) light.
EAM Import::2019-03-14

Flying particle microlaser and temperature sensor in hollow-core photonic crystal fiber - Zeltner, Richard; Pennetta, Riccardo; Xie, Shangran; Russell, Philip St. John (Optics Letters, 2018)
Whispering-gallery mode (WGM) resonators combine small optical mode volumes with narrow resonance linewidths, making them exciting platforms for a variety of applications. Here we report a flying WGM microlaser, realized by optically trapping a dye-doped microparticle within a liquid-filled hollow-core photonic crystal fiber (HC-PCF) using a CW laser and then pumping it with a pulsed excitation laser whose wavelength matches the absorption band of the dye. The laser emits into core-guided modes that can be detected at the endfaces of the HC-PCF. Using radiation forces, the microlaser can be freely propelled along the HC-PCF over multi-centimeter distances-orders of magnitude farther than in previous experiments where tweezers and fiber traps were used. The system can be used to measure temperature with high spatial resolution, by exploiting the temperature-dependent frequency shift of the lasing modes, and may also permit precise delivery of light to remote locations.
EAM Import::2019-03-14

Flying Particle Thermosensor in Hollow-Core Fiber Based on Fluorescence Lifetime Measurements - Freitag, Jasper; Köppel, Max; Romodina, Maria N.; Joly, Nicolas; Schmauß, Bernhard (IEEE Journal of Selected Topics in Quantum Electronics, 2023)
Keywords: frequency-domain fluorescence lifetime; hollow-core fiber; optical trapping; flying particle temperature sensor

Flying triangulation - A motion-robust optical 3D sensor for the real-time shape acquisition of complex objects - Häusler, Gerd; Ettl, Svenja; Arold, Oliver; Yang, Zheng (Applied Optics, 2012)
Three-dimensional (3D) shape acquisition is difficult if an all-around measurement of an object is desired or if a relative motion between object and sensor is unavoidable. An optical sensor principle is presented-we call it "flying triangulation"-that enables a motion-robust acquisition of 3D surface topography. It combines a simple handheld sensor with sophisticated registration algorithms. An easy acquisition of complex objects is possible-just by freely hand-guiding the sensor around the object. Real-time feedback of the sequential measurement results enables a comfortable handling for the user. No tracking is necessary. In contrast to most other eligible sensors, the presented sensor generates 3D data from each single camera image.
Keywords: optical 3D metrology; motion robust; triangulation

Focusing characteristics of a 4pi parabolic mirror light-matter interface - Alber, Lucas; Fischer, Martin; Bader, Marianne; Mantel, Klaus; Sondermann, Markus; Leuchs, Gerd (arXiv, 2016)

Focusing characteristics of a 4π parabolic mirror light-matter interface - Alber, Lucas; Fischer, Martin; Bader, Marianne; Mantel, Klaus; Sondermann, Markus; Leuchs, Gerd (Journal of the European Optical Society: Rapid Publications, 2017)

Focusing light to a tighter spot - Leuchs, Gerd; et al. (Optics Communications, 2000)
The smallest spot sizes are reached by focusing an annular shaped light beam with a high aperture lens. We show theoretically that the focal area is further reduced when using a novel radially polarized instead of a linearly polarized light annulus. In the vicinity of the focus there is a large longitudinally polarized field component which is still narrower and has no pronounced side lobes. A special photosensitive layer prepared to be sensitive only to this longitudinal field component may be used to reach an even smaller focal area, 0.1 λ2, which is determined by the contour of the intensity distribution at half the maximum value. The radially polarized doughnut mode may also be used to build improved near field sensors having a substantially increased brightness.
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.focusi

Form assessment of hollow cylindrical specimens - Lindlein, Norbert; et al. (Applied Optics, 2002)
Grazing-incidence interferometry that makes use of diffractive axicons for the measurement of cylindrical mantle surfaces has already been reported. However, measurement of concave rod structures poses a severe problem because these structures are subject to spurious fringes caused by parasitic diffraction orders of the diffractive axicons. By breaking the symmetry of the interferometric setup it is possible to obtain unique interferograms of the inner mantle surfaces of hollow cylinders as cages for roller bearings or other workpieces produced on lathe machines that have a suitable surface finish. Special design issues for the computer-generated holograms and the interferometric setup are discussed, and test examples are given. © 2002 Optical Society of America.
UnivIS-Import:2015-04-14:Pub.2002.nat.dphy.optik.1optik.formas

Formation of optical supramolecular structures in a fibre laser by tailoring long-range soliton interactions - He, Wenbin; Pang, Meng; Yeh, Dung-Han; Huang, Jiapeng; Menyuk, C. R.; Russell, Philip St. John (Nature Communications, 2019)
Self-assembly of fundamental elements through weak, long-range interactions plays a central role in both supramolecular DNA assembly and bottom-up synthesis of nanostructures. Optical solitons, analogous in many ways to particles, arise from the balance between nonlinearity and dispersion and have been studied in numerous optical systems. Although both short- and long-range interactions between optical solitons have attracted extensive interest for decades, stable soliton supramolecules, with multiple aspects of complexity and flexibility, have thus far escaped experimental observation due to the absence of techniques for enhancing and controlling the long-range inter-soliton forces. Here we report that long-range soliton interactions originating from optoacoustic effects and dispersive-wave radiations can be precisely tailored in a fibre laser cavity, enabling self-assembly of large numbers of optical solitons into highly-ordered supramolecular structures. We demonstrate several features of such optical structures, highlighting their potential applications in optical information storage and ultrafast laser-field manipulation.
CRIS-Team Scopus Importer:2019-12-27

Form birefringent quarter wave plate for polarization conversion - Ghadyani, Zahra; Rothau, Sergej; Russina, Olga; Harder, Irina; Lindlein, Norbert (37th International Conference on Micro and Nano Engineering, 2011)

Fortschritte bei der Automatisierung des Reverse Engineering - Häusler, Gerd; et al. (Optische Formerfassung, 1997)
UnivIS-Import:2015-04-16:Pub.1997.nat.dphy.optik.1optik.fortsc

Four-state discrimination scheme beyond the heterodyne limit - Müller, Christian R.; Usuga, Mario A.; Wittmann, Christoffer; Takeoka, Masahiro; Marquardt, Christoph; Andersen, Ulrik L.; Leuchs, Gerd (2012 Conference on Lasers and Electro-Optics, CLEO 2012, 2012)
We propose and experimentally demonstrate a hybrid discrimination scheme for the quadrature phase shift keying protocol, which outperforms heterodyne detection for any signal power. The discrimination is composed of a quadrature measurement, feed forward and photon detection. © 2012 OSA.
CRIS-Team Scopus Importer:2022-06-05

Fractional Talbot effect for periodic microlens arrays - Lindlein, Norbert; et al. (Optical Engineering, 1997)
It is well known that the foci of a periodic array of microlenses are reproduced and multiplied in the fractional Talbot planes. But the intensity between the multiplied foci varies in general in one period, especially if the light in the spacing between the lenses is not absorbed but transmitted. Additionally, in the case of microlenses with a high numerical aperture the parabolic approximation or Fresnel diffraction, which is normally used to explain the Talbot effect, is no longer valid. A theoretical explanation and numerical simulations are given together with experimental results. © 1997 Society of Photo-Optical Instrumentation Engineers.
UnivIS-Import:2015-03-05:Pub.1997.nat.dphy.optik.1optik.fracti
Keywords: Array illuminator; Fractional Talbot effect; Intensity of foci; Microlens arrays; Propagation of angular spectrum; Self-imaging

Free-space propagation of high-dimensional structured optical fields in an urban environment - Lavery, Martin P. J.; Peuntinger, Christian; Günthner, Kevin; Banzer, Peter; Elser, Dominique Alexander; Boyd, Robert W.; Padgett, Miles J.; Marquardt, Christoph; Leuchs, Gerd (Science Advances, 2017)
Spatially structured optical fields have been used to enhance the functionality of a wide variety of systems that use light for sensing or information transfer. As higher-dimensional modes become a solution of choice in optical systems, it is important to develop channel models that suitably predict the effect of atmospheric turbulence on these modes. We investigate the propagation of a set of orthogonal spatial modes across a free-space channel between two buildings separated by 1.6 km. Given the circular geometry of a common optical lens, the orthogonal mode set we choose to implement is that described by the Laguerre-Gaussian (LG) field equations. Our study focuses on the preservation of phase purity, which is vital for spatial multiplexing and any system requiring full quantum-state tomography. We present experimental data for the modal degradation in a real urban environment and draw a comparison to recognized theoretical predictions of the link. Our findings indicate that adaptations to channel models are required to simulate the effects of atmospheric turbulence placed on high-dimensional structured modes that propagate over a long distance. Our study indicates that with mitigation of vortex splitting, potentially through precorrection techniques, one could overcome the challenges in a real point-to-point free-space channel in an urban environment.
CRIS-Team Scopus Importer:2022-06-05

Free space quantum communication using continuous polarization variables - Heim, Bettina; Peuntinger, Christian; Wittmann, Christoffer; Marquardt, Christoph; Leuchs, Gerd (Optics InfoBase Conference Papers, 2011)
We experimentally investigate atmospheric influences on quantum communication using continuous polarization variables. Signal and local oscillator are combined in one spatial mode, which leads to excellent interference at the homodyne detection. Phase fluctuations are thus auto-compensated. © 2011 Optical Society of America.
CRIS-Team Scopus Importer:2022-06-05

Free-space quantum links under diverse weather conditions - Vasylyev, Dmytro Yu.; Semenov, A. A.; Vogel, W.; Guenthner, K.; Thurn, Andreas; Bayraktar, O.; Marquardt, Christoph (Physical Review A, 2017)
Free-space optical communication links are promising channels for establishing secure quantum communication. Here we study the transmission of nonclassical light through a turbulent atmospheric link under diverse weather conditions, including rain or haze. To include these effects, the theory of light transmission through atmospheric links in the elliptic-beam approximation presented by Vasylyev et al. [D. Vasylyev, Phys. Rev. Lett. 117, 090501 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.090501] is further generalized. It is demonstrated, with good agreement between theory and experiment, that low-intensity rain merely contributes additional deterministic losses, whereas haze also introduces additional beam deformations of the transmitted light. Based on these results, we study theoretically the transmission of quadrature squeezing and Gaussian entanglement under these weather conditions.
CRIS-Team Scopus Importer:2022-06-05

Free-Space Quantum Signatures Using Heterodyne Measurements - Croal, Callum; Peuntinger, Christian; Heim, Bettina; Khan, Imran; Marquardt, Christoph; Leuchs, Gerd; Wallden, Petros; Andersson, Erika; Korolkova, Natalia (Physical Review Letters, 2016)
Digital signatures guarantee the authorship of electronic communications. Currently used "classical" signature schemes rely on unproven computational assumptions for security, while quantum signatures rely only on the laws of quantum mechanics to sign a classical message. Previous quantum signature schemes have used unambiguous quantum measurements. Such measurements, however, sometimes give no result, reducing the efficiency of the protocol. Here, we instead use heterodyne detection, which always gives a result, although there is always some uncertainty. We experimentally demonstrate feasibility in a real environment by distributing signature states through a noisy 1.6 km free-space channel. Our results show that continuous-variable heterodyne detection improves the signature rate for this type of scheme and therefore represents an interesting direction in the search for practical quantum signature schemes. For transmission values ranging from 100% to 10%, but otherwise assuming an ideal implementation with no other imperfections, the signature length is shorter by a factor of 2 to 10. As compared with previous relevant experimental realizations, the signature length in this implementation is several orders of magnitude shorter.
CRIS-Team Scopus Importer:2022-06-05

Frenet–Serret analysis of helical Bloch modes in N-fold rotationally symmetric rings of coupled spiraling optical waveguides - Chen, Y.; Russell, Philip St. John (Journal of the Optical Society of America B-Optical Physics, 2021)
The behavior of electromagnetic waves in chirally twisted structures is a topic of enduring interest, dating back at least to the 1940s invention of the microwave travelling-wave-tube amplifier and culminating in contemporary studies of chiral metamaterials, metasurfaces, and photonic crystal fibers (PCFs). Optical fibers with chiral microstructures, drawn from a spinning preform, have many useful properties, exhibiting, for example, circular birefringence and circular dichroism. It has recently been shown that chiral fibers with N-fold rotationally symmetric (symmetry group CN) transverse microstructures support families of helical Bloch modes (HBMs), each of which consists of a superposition of azimuthal Bloch harmonics (or optical vortices). An example is a fiber with N coupled cores arranged in a ring around its central axis (N-core single-ring fiber). Although this type of fiber can be readily modeled using scalar coupled-mode theory, a full description of its optical properties requires a vectorial analysis that takes account of the polarization state of the light, which is particularly important in studies of circular and vortical birefringence. In this paper, we develop, using an orthogonal 2D helicoidal coordinate system embedded in a cylindrical surface at constant radius, a rigorous vector coupled-mode description of the fields using local Frenet–Serret frames that rotate and twist with each of the N cores. The analysis places on a firm theoretical footing a previous HBM theory in which a heuristic approach was taken, based on physical intuition of the properties of Bloch waves. After a detailed review of the polarization evolution in a single spiraling core, analysis of the N-core single-ring system is carefully developed step by step. Accuracy limits of the analysis are assessed by comparison with the results of finite element modeling, focusing in particular on the dispersion, polarization states, and transverse field profiles of the HBMs. We believe this study provides clarity into what can sometimes be a rather difficult field and will facilitate further exploration of real-world applications of these fascinating waveguiding systems.
CRIS-Team Scopus Importer:2021-04-23