Mehr Sicherheit durch Quantenschlüssel - Leuchs, Gerd; et al. (Zeitschrift für Physik, 2003)
UnivIS-Import:2015-03-09:Pub.2003.nat.dphy.optik.1optik.mehrsi

Mehrwellenlängen-Interferometrie zur absoluten Abstandsmessung und 3D-Bildgebung - Leuchs, Gerd; et al. (Technisches Messen, 2000)
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.mehrwe

Messen ohne Auszuspannen - Langer Lasertaster für Schleifmaschinen - Leuchs, Gerd; et al. (Kontrolle : Qualitätssicherung in der Produktion, 1996)
UnivIS-Import:2015-03-05:Pub.1996.nat.dphy.optik.1optik.messen

METASURFACES for quantum technologies - Wang, Kai; Chekhova, Maria; Kivshar, Yuri (Physics Today, 2022)
CRIS-Team WoS Importer:2022-09-16

Metrical calibration of a Phase measuring triangulation sensors - Häusler, Gerd; et al. (Proceedings of the Vision Modeling and Visualization Conference 2001, 2000)
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.metric

Metrology of laser-guided particles in air-filled hollow-core photonic crystal fiber - Schmidt, O. A.; Garbos, M. K.; Euser, T. G.; Russell, Philip St. John (Optics Letters, 2012)
Micrometer-sized particles are trapped in front of an air-filled hollow-core photonic crystal fiber using a novel dual-beam trap. A backward guided mode produces a divergent beam that diffracts out of the core, and simultaneously a focused laser beam launches a forward-propagating mode into the core. By changing the backward/forward power balance, a trapped particle can be selectively launched into the hollow core. Once inside, particles can be optically propelled along several meters of fiber with mobilities as high as 19 cm·s-1 W-1 (precisely measured using in-fiber Doppler velocimetry). The results are in excellent agreement with theory. The system allows determination of fiber loss as well as the mass density and refractive index of single particles.
EAM Import::2019-03-12

Microconstriction Arrays for High-Throughput Quantitative Measurements of Cell Mechanical Properties - Lange, Janina; Steinwachs, Julian; Kolb, Thorsten; Lautscham, Lena; Harder, Irina; Whyte, Graeme; Fabry, Ben (Biophysical Journal, 2015)

Micro-cylinder-lens testing using computer-generated holograms - Mantel, Klaus Peter; Lamprecht, Jürgen; Lindlein, Norbert; Schreiner, Roland; Schwider, Johannes; Ferstl, Manfred (Fringe 2001, 2001)
UnivIS-Import:2015-04-16:Pub.2001.nat.dphy.optik.1optik.microc

Microdeflectometry - a novel tool to acquire three-dimensional microtopography with nanometer height resolution - Häusler, Gerd; Richter, Claus; Leitz, Karl-Heinz; Knauer, Markus C. (Optics Letters, 2008)
We introduce "microdeflectometry," a novel technique for measuring the microtopography of specular surfaces. The primary data are the local slope of the surface under test. Measuring the slope instead of the height implies high information efficiency and extreme sensitivity to local shape irregularities. The lateral resolution can be better than 1 μm, whereas the resulting height resolution is in the range of 1 nm. Microdeflectometry can be supplemented by methods to expand the depth of field, with the potential to provide quantitative 3D imaging with scanning-electron-microscope-like features. © 2008 Optical Society of America.
LFT Import::2019-07-29 (1515)

Microfluidic integration of photonic crystal fibers for online photochemical reaction analysis - Unterkofler, S.; Mcquitty, R. J.; Euser, T. G.; Farrer, N. J.; Sadler, P. J.; Russell, Philip St. John (Optics Letters, 2012)
Liquid-filled hollow-core photonic crystal fibers (HC-PCFs) are perfect optofluidic channels, based on their unique feature of low loss optical guidance in a liquid medium. Thereby, the overlap of the dissolved specimen and the intense light field in the micron-sized core is increased manifold as compared to conventional bioanalytical techniques, facilitating highly efficient photoactivation processes. Here we introduce a novel integrated analytical technology for photochemistry by microfluidic coupling of a HC-PCF nanoflow reactor to supplementary detection devices. Applying a continuous flow through the fiber, we deliver photochemical reaction products to a mass spectrometer in an online and hence rapid fashion, which is highly advantageous over conventional cuvette-based approaches.
EAM Import::2019-03-12

Microlens laser beam homogenizer - From theory to application - Zimmermann, Maik; Lindlein, Norbert; Völkl, Ralf; Weible, Ken (Laser Beam Shaping VIII, 2007)
Many applications in laser manufacturing like semiconductor lithography, micro-machining, micro-structuring or material-analysis require a homogeneous intensity distribution of the laser beam over its complete profile. Refractive and diffractive beam homogenizer solutions have been developed for this challenge, but their applicability strongly depends on the physics of the individual laser beam. This paper investigates the influence of laser beam properties like spatial coherence for microlens beam homogenizers. Diffraction at the small lens apertures and interference effects of periodic arrays are explained by using diffraction theory. Different microlens beam homogenizer configurations are presented. Design considerations that might be helpful for the layout of a specific microlens beam homogenizer system are discussed. It is shown that, among other factors, the Fresnel number is the most important quantity to characterize the influence of diffraction effects on microlens laser beam homogenizers. The influence of the spatial partial coherence will be explained for the example of a Fly's eye condenser. For cw laser sources, the influence of a rotating diffuser plate on grating interference and speckles effects is investigated. Finally, the theory will be compared to some practical examples in planar laser measurement techniques, in combustion diagnostics and micromachining with Excimer laser
LFT Import::2019-08-05 (1478)
Keywords: Coherence; Diffraction; Diffuser; Flat-top; Homogenizer; Laser; Microlens; Shaping

Microscale Generation of Entangled Photons without Momentum Conservation - Okoth, Cameron; Cavanna, Andrea; Santiago-Cruz, T.; Chekhova, Maria (Physical Review Letters, 2019)
We report, for the first time, the observation of spontaneous parametric down-conversion (SPDC) free of phase matching (momentum conservation). We alleviate the need to conserve momentum by exploiting the position-momentum uncertainty relation and using a planar geometry source, a 6 μm thick layer of lithium niobate. Nonphase-matched SPDC opens up a new platform on which to investigate fundamental quantum effects but it also has practical applications. The ultrasmall thickness leads to a frequency spectrum an order of magnitude broader than that of phase-matched SPDC. The strong two-photon correlations are still preserved due to energy conservation. This results in ultrashort temporal correlation widths and huge frequency entanglement. The studies we make here can be considered as the initial steps into the emerging field of nonlinear quantum optics on the microscale and nanoscale.
CRIS-Team Scopus Importer:2020-02-21

Microsphere kinematics from the polarization of tightly focused nonseparable light - Berg-Johansen, Stefan; Neugebauer, Martin; Aiello, Andrea; Leuchs, Gerd; Banzer, Peter; Marquardt, Christoph (Optics Express, 2021)
Recently, it was shown that vector beams can be utilized for fast kinematic sensing via measurements of their global polarization state [Optica 2, 864 (2015)]. The method relies on correlations between the spatial and polarization degrees of freedom of the illuminating field which result from its nonseparable mode structure. Here, we extend the method to the nonparaxial regime. We study experimentally and theoretically the far-field polarization state generated by the scattering of a dielectric microsphere in a tightly focused vector beam as a function of the particle position. Using polarization measurements only, we demonstrate position sensing of a Mie particle in three dimensions. Our work extends the concept of back focal plane interferometry and highlights the potential of polarization analysis in optical tweezers employing structured light.
CRIS-Team Scopus Importer:2021-04-30

Microwave Quantum Optics with Superconducting Circuits: From Quantum Variational Algorithms to Sensitive Electron Spin Resonance (ESR) Measurements - Eichler, Christopher (Resonator QED Conference, 2017)
The high level of control achievable over quantized degrees of freedom has turned superconducting circuits into one of the prime physical architectures for quantum computing and simulation. Along with the continuing progress towards building a universal quantum computer, the availability of small-scale quantum devices has raised interest in hybrid quantum-classical algorithms, in which the power of quantum computation is combined with classical optimization [1]. In my talk, I will present an experimental realization of this idea based on the controlled generation of matrix product states (MPS) – a class of states which has proven extremely powerful as a variational ansatz for numerical simulations. The correlation properties of these states are used to experimentally find the ground state of an interacting Bose gas confined in one dimension [2]. Our findings reveal interesting connections between the physics of cavity QED, solid state theory, and quantum information science. Extensions of the presented approach may be envisaged to also explore dynamical phenomena and discrete lattice models, offering interesting interdisciplinary perspectives. Technologically crucial for our experiments have been the development of quantum limited amplifiers [3] and the ability to measure photon statistics in the microwave frequency range [4]. Apart from being essential in our quest to build a practical quantum simulation platform, these technologies turn out very useful for exploring other systems such as spins and electrons in semiconductors [5,6]. [1] S. Barret et al., PRL 110, 090501 (2013), J.R. McClean et al., NJP 18, 023023, (2016) [2] C. Eichler et al., Phys. Rev. X 5, 041044 (2015) [3] C. Eichler et al. Phys. Rev. Lett. 106, 220503 (2011), C. Eichler et al. PRA 86, 032106 (2012) [4] C. Eichler et al., PRL 113, 110502 (2014), C. Eichler et al., PRL 107, 113601 (2011) [5] Y. Liu, et al., Science 347, 258 (2015), J. Stehlik et al., Phys. Rev. Applied 4, 014018 (2015) [6] Eichler et al., Phys. Rev. Lett. 118, 037701 (2017)
Keywords: wwwqudev

Mimicking chiral light-matter interaction - Nechayev, Sergey; Banzer, Peter (Physical Review B, 2019)
We demonstrate that achiral electric-dipole scatterers can mimic an interaction of light with chiral matter by generating far-field circular polarization upon scattering, even though the optical chirality of the incident field as well as that of the scattered light is zero. On the one hand, the presented effect originates from the fact that electric-dipole scatterers respond selectively only to the incident electric field, which eventually results in depolarization of the transmitted beam and in generation of far-field circular polarization. On the other hand, although the incident beam does not possess any optical chirality, it lacks reflection symmetry and therefore it is geometrically chiral. To experimentally demonstrate this effect, we utilize a cylindrical vector beam with spiral polarization and a spherical gold nanoparticle positioned on the optical axis-the axis of rotational symmetry of the system. Our experiment and a simple theoretical model address the fundamentals of duality symmetry in optics and chiral light-matter interactions, accentuating their richness and ubiquity yet in highly symmetric configurations.
CRIS-Team WoS Importer:2019-06-25

Misalignment effects of the Shack-Hartmann sensor - Lindlein, Norbert; et al. (Applied Optics, 1997)
UnivIS-Import:2015-03-05:Pub.1997.nat.dphy.optik.1optik.misali

Misalignment effects of the shack–hartmann sensor - Lindlein, Norbert; et al. (Applied Optics, 1998)
The Shack–Hartmann sensor uses a microlens array and a CCD camera for wave–front measurements. To obtain wave–front measurements with high accuracy, an accurate relative alignment of both is essential. The different states of misalignment of the Shack–Hartmann sensor are divided into groups and are treated theoretically and experimentally. Their effect on the accuracy of wave–front measurements is evaluated. In addition, a practical method for proper alignment of the Shack–Hartmann sensor is proposed. © 1998 Optical Society of America.

Mode-hop-free tunable optical parametric oscillator utilizing a whispering gallery mode resonator - Förtsch, Michael; Schunk, Gerhard; Sedlmeir, Florian; Fürst, Josef; Wittmann, Christoffer; Strekalov, Dmitry; Schwefel, Harald G.L.; Marquardt, Christoph; Leuchs, Gerd (2012 Conference on Lasers and Electro-Optics, CLEO 2012, 2012)
We report on a compact and stable optical parametric oscillator in a whispering gallery mode resonator, that combines very low pump thresholds with versatile tunability. © 2012 OSA.
CRIS-Team Scopus Importer:2022-06-05

Modeling, Simulation and Manufacturing of Polymer Optical Waveguides by Using the OPTAVER Process - Reitberger, Thomas; Zeitler, Jochen Tobias; Backhaus, Carsten; Hoffmann, Gerd-Albert; Wienke, Alexander; Lorenz, Lukas; Bock, Karlheinz; Wolter, Klaus-Jürgen; Suttmann, Oliver; Overmeyer, Ludger; Lindlein, Norbert; Franke, Jörg (Applied Industrial Optics: Spectroscopy, Imaging and Metrology 2019, 2019)
This paper shows the modeling, simulation and production of polymer optical waveguides using the OPTAVER process. The additive manufactured multimode waveguides with their typical cross-section of a circle shape are of low cost and high-performance.<br

Modeling the dielectric function of degenerately doped ZnO: Al thin films grown by ALD using physical parameters - Latzel, Michael; Göbelt, Manuela; Brönstrup, Gerald; Venzago, Cornel; Schmitt, W.; Sarau, George; Christiansen, Silke (Optical Materials Express, 2015)
Transparent conductive thin films are a key building block of modern optoelectronic devices. A promising alternative to expensive indium containing oxides is aluminum doped zinc oxide (AZO). By correlating spectroscopic ellipsometry and photoluminescence, we analyzed the contributions of different optical transitions in AZO grown by atomic layer deposition to a model dielectric function (MDF) over a wide range of photon energies. The derived MDF reflects the effects of the actual band structure and therefore describes the optical properties very accurately. The presented MDF is solely based on physically meaningful parameters in contrast to empirical models like e.g. the widely used Sellmeier equation, but nevertheless real and imaginary parts are expressed as closed-form expressions. We analyzed the influence of the position of the Fermi energy and the Fermi-edge singularity to the different parts of the MDF. This information is relevant for design and simulation of optoelectronic devices and can be determined by analyzing the results from spectroscopic ellipsometry.

Mode structure and photon number correlations in squeezed quantum pulses - Leuchs, Gerd; et al. (Physical Review A, 2002)
Knowing the answer to the question of what is the complete quantum description of a pulse would be very helpful in quantum information processing: one could fully utilize the squeezing and entanglement properties of the sources. After forming a soliton pulse in a fiber, one can determine its multimode quantum state in the most comprehensive way. Hence, one can then optimize the medium properties to achieve maximum squeezing, or the maximum purity of an entangled state.
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.modest

Modifications of the coherence radar for in vivo profilometry in dermatology - Häusler, Gerd; et al. (SPIE j, 1998)
UnivIS-Import:2015-03-05:Pub.1998.nat.dphy.optik.1optik.modifi

Modulational-instability-free pulse compression in anti-resonant hollow-core photonic crystal fiber - Kottig, Felix; Tani, Francesco; Russell, Philip St. John (Optics Letters, 2020)
Gas-filled hollow-core photonic crystal fiber (PCF) is used for efficient nonlinear temporal compression of femtosecond laser pulses, two main schemes being direct soliton-effect self-compression and spectral broadening followed by phase compensation. To obtain stable compressed pulses, it is crucial to avoid decoherence through modulational instability (MI) during spectral broadening. Here, we show that changes in dispersion due to spectral anti-crossings between the fundamental-core mode and core wall resonances in anti-resonant-guiding hollow-core PCF can strongly alter the MI gain spectrum, enabling MI-free pulse compression for optimized fiber designs. The results are important, since MI cannot always be suppressed by pumping in the normal dispersion regime. (C) 2020 Optical Society of America
CRIS-Team WoS Importer:2020-08-14

Möglichkeiten und Grenzen optischer 3D-Sensoren in der industriellen Praxis - Häusler, Gerd (Optische Messtechnik an diffus reflektierenden Medien, 1997)
UnivIS-Import:2015-04-20:Pub.1997.nat.dphy.optik.1optik.mglich

Molecular Mie model for second harmonic generation and sum frequency generation - Wunderlich, Sarina; Schürer, Benedikt; Sauerbeck, Christian; Peukert, Wolfgang; Peschel, Ulf (Physical Review B, 2011)
A theoretical model to simulate second harmonic and sum frequency generation from stratified spherical particles of arbitrary material is presented and compared with the widely used Rayleigh-Gans-Debye approximation and to experimental results from polystyrene particles with adsorbed malachite green molecules. In this model, the nonlinear polarization is caused by individual dipoles placed in the vicinity of the sphere and is simulated on a molecular basis. This offers greater flexibility to model more sophisticated systems.

Molecule-photon interactions in phononic environments - Reitz, Michael; Sommer, C.; Gurlek, B.; Sandoghdar, Vahid; Martin-Cano, D.; Genes, C. (Physical Review Research, 2020)
Molecules constitute compact hybrid quantum optical systems that can interface photons, electronic degrees of freedom, localized mechanical vibrations, and phonons. In particular, the strong vibronic interaction between electrons and nuclear motion in a molecule resembles the optomechanical radiation pressure Hamiltonian. While molecular vibrations are often in the ground state even at elevated temperatures, one still needs to get a handle on decoherence channels associated with phonons before an efficient quantum optical network based on optovibrational interactions in solid-state molecular systems could be realized. As a step towards a better understanding of decoherence in phononic environments, we take here an open quantum system approach to the nonequilibrium dynamics of guest molecules embedded in a crystal, identifying regimes of Markovian versus non-Markovian vibrational relaxation. A stochastic treatment, based on quantum Langevin equations, predicts collective vibron-vibron dynamics that resembles processes of sub- and super-radiance for radiative transitions. This in turn leads to the possibility of decoupling intramolecular vibrations from the phononic bath, allowing for enhanced coherence times of collective vibrations. For molecular polaritonics in strongly confined geometries, we also show that the imprint of optovibrational couplings onto the emerging output field results in effective polariton cross-talk rates for finite bath occupancies.
CRIS-Team WoS Importer:2021-01-22

Monitoring of catalytic reactions in photonic crystal fiber - Cubillas, Ana Maria; Schmidt, Matthias; Scharrer, Michael; Euser, T. G.; Etzold, Bastian; Taccardi, Nicola; Wasserscheid, Peter; Russell, Philip St. John (2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011, 2011)
Hollow-core photonic crystal fiber (HC-PCF) offers several advantages for chemical analysis, for example, long optical pathlengths, sub-L sample volumes, close to 100% overlap between light and sample, and more compact systems for sensing [1-2] and photochemistry [3-4]. Here we compare the performance of a conventional cuvette-based UV-VIS system for monitoring of catalytic reactions with a system based on liquid-filled HC-PCF. We study the photo-Fenton catalytic reaction, which under visible light irradiation induces degradation of methylene blue dye (MB) in the presence of Fe2+ / H2O 2 [5]. © 2011 IEEE.
CRIS-Team Scopus Importer:2023-08-15

More Than 34 dB Backscattering Suppression in Microresonators - Svela, Andreas O.; Silver, Jonathan M.; Del Bino, Leonardo; Zhang, Shuangyou; Woodley, Michael T.M.; Vanner, Michael R.; Del'Haye, Pascal (2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021, 2021)
Optical modes in whispering-gallery-mode (WGM) resonators generally come in pairs of degenerate modes with opposite propagation directions: a clockwise and a counter-clockwise mode. However, sub-wavelength-size imperfections on the surface and in the bulk material of the resonators, usually cause some amount of Rayleigh scattering between the modes [1]. For sufficiently high levels of backscattering, the coupling between the modes can be observed as a resolvable splitting in the frequency domain [2]. Coupling of the modes is unfavourable for some WGM resonator applications, for example gyroscopes [3] , dual frequency combs [4] , and applications relying on symmetry breaking of counter-propagating light [5] , [6].
CRIS-Team Scopus Importer:2021-10-29

Multilevel amplitude and phase regeneration in a nonlinear amplifying loop mirror with a phase-sensitive amplifier - Röthlingshöfer, Tobias; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Transparent Optical Networks (ICTON), 2012)
A novel regenerator scheme for all-optical multilevel simultaneous amplitude and phase noise suppression is proposed. For a star-8QAM signal, consisting of two amplitude and four phase states, EVM reduction is 4 dB and 2.5 dB for the high- and low-power states, respectively. The limiting effects of the regenerator performance have been considered.
lhft_intern.bib::Roethlingshoefer2012cb

Multilevel Phase-Preserving Amplitude Regeneration Using a Single Nonlinear Amplifying Loop Mirror - Hierold, Martin; Roethlingshoefer, Tobias; Sponsel, Klaus; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE Photonics Technology Letters, 2011)
lhft_intern.bib::Hierold2011

Multimode optical parametric amplification in the phase-sensitive regime - Frascella, Gaetano; Zakharov, R. V.; Tikhonova, O. V.; Chekhova, Maria (Optics Letters, 2021)
Phase-sensitive optical parametric amplification of squeezed states helps to overcome detection loss and noise and thus increases the robustness of sub-shot-noise sensing. Because such techniques, e.g., imaging and spectroscopy, operate with multimode light, multimode amplification is required. Here we find the optimal methods for multimode phase-sensitive amplification and verify them in an experiment where a pumped second-order nonlinear crystal is seeded with a Gaussian coherent beam. Phase-sensitive amplification is obtained by tightly focusing the seed into the crystal, rather than seeding with close-to-plane waves. This suggests that phase-sensitive amplification of sub-shot-noise images should be performed in the near field. A similar recipe can be formulated for the time and frequency, which makes this work relevant for quantum-enhanced spectroscopy.
CRIS-Team Scopus Importer:2021-05-21

Multimode Quantum Correlations - Leuchs, Gerd; et al. (Coherence and Statistics of Photons and Atoms, 2001)
UnivIS-Import:2015-04-20:Pub.2001.nat.dphy.optik.1optik.multim

Multi-pass Shack-Hartmann planeness test: monitoring thermal stress - Schwider, Johannes; Leuchs, Gerd (Optics Express, 2010)

Multiphoton effects with bright squeezed vacuum - Kopylov, D. A.; Spasibko, K. Yu; Cutipa, P.; Murzina, T. V.; Chekhova, Maria (Optics InfoBase Conference Papers, 2020)
Light generated through strongly pumped parametric down-conversion has extremely strong photon-number fluctuations and is therefore highly efficient for multiphoton effects. In addition, its spectral and spatial properties can be tailored to allow two-dimensional multiphoton spectroscopy.
CRIS-Team Scopus Importer:2020-11-13

Multiphoton electron emission with non-classical light - Heimerl, Jonas; Mikhaylov, Alexander; Meier, Stefan; Höllerer, Henrick; Kaminer, Ido; Chekhova, Maria; Hommelhoff, Peter (Nature Physics, 2024)
Photon number distributions of classical and non-classical light sources have been studied extensively, yet their impact on photoemission processes is largely unexplored. In this article, we present measurements of electron number distributions from metal needle tips illuminated with ultrashort light pulses with various photon quantum statistics. By varying the photon statistics of the exciting light field between classical (Poissonian) and quantum (super-Poissonian), we demonstrate that the measured electron distributions are changed substantially. Using single-mode bright squeezed vacuum light, we measure extreme statistics events with up to 65 electrons from one light pulse at a mean of 0.27 electrons per pulse—the likelihood for such an event equals 10−128 with Poissonian statistics. By changing the number of modes of the exciting bright squeezed vacuum, we can tailor the electron number distribution on demand. Most importantly, our results demonstrate that the photon statistics is imprinted from the driving light to the emitted electrons, opening the door to new sensor devices and to strong-field optics with quantum light and electrons.<br
Keywords: Nanophotonics and plasmonics; Nonlinear optics; Quantum optics

Multiple-Wavelength Interferometry for Absolute Distance Measurement and Three-Dimentional Imaging - Leuchs, Gerd; et al. (Technisches Messen, 2000)
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.multip

Multipolar hierarchy of efficient quantum polarization measures - De La Hoz, Pablo; Klimov, A. B.; Bjork, G.; Kim, Y. -H.; Mueller, C.; Marquardt, Christoph; Leuchs, Gerd; Sanchez-Soto, L. L.; Marquardt, Christoph (Physical Review A - Atomic, Molecular, and Optical Physics, 2013)
We advocate a simple multipole expansion of the polarization density matrix. The resulting multipoles appear as successive moments of the Stokes variables and can be obtained from feasible measurements. In terms of these multipoles we construct a whole hierarchy of measures that accurately assess higher-order polarization fluctuations. © 2013 American Physical Society.
CRIS-Team Scopus Importer:2022-06-05

Multi-twist polarization ribbon topologies in highly-confined optical fields - Bauer, Thomas; Banzer, Peter; Bouchard, Frederic; Orlov, Sergej; Marrucci, Lorenzo; Santamato, Enrico; Boyd, Robert W.; Karimi, Ebrahim; Leuchs, Gerd (New Journal of Physics, 2019)
Electromagnetic plane waves, solutions to Maxwell's equations, are said to be 'transverse' in vacuum. Namely, the waves' oscillatory electric and magnetic fields are confined within a plane transverse to the waves' propagation direction. Under tight-focusing conditions however, the field can exhibit longitudinal electric or magnetic components, transverse spin angular momentum, or non-trivial topologies such as Mobius strips. Here, we show that when a suitably spatially structured beam is tightly focused, a three-dimensional polarization topology in the form of a ribbon with two full twists appears in the focal volume. We study experimentally the stability and dynamics of the observed polarization ribbon by exploring its topological structure for various radii upon focusing and for different propagation planes.
CRIS-Team WoS Importer:2019-05-24

Mutually unbiased bases and generalized Bell states - Leuchs, Gerd; et al. (Physical Review A, 2009)
We employ a straightforward relation between mutually unbiased and Bell bases to extend the latter in terms of a direct construction for the former. We analyze in detail the properties of these generalized Bell states, showing that they constitute an appropriate tool for testing entanglement in bipartite multiqudit systems. © 2009 The American Physical Society.
UnivIS-Import:2015-04-14:Pub.2009.nat.dphy.optik.1optik.mutual

Nanobore PCF maintaining cylindrically polarized modes - Euser, T. G.; Joly, N. Y.; Gabriel, C.; Marquardt, Christoph; Zang, L. Y.; Banzer, P.; Brenn, A.; Elser, D.; Förtsch, M.; Rammler, S.; Scharrer, M.; Leuchs, Gerd; et al. (Optics InfoBase Conference Papers, 2010)
A nanoscale hole placed centrally in the core of a PCF breaks the degeneracy between radially and azimuthally polarized modes, causing a large splitting in phase velocity, group velocity and dispersion. © 2010 Optical Society of America.
CRIS-Team Scopus Importer:2022-06-05

Nanometer Precision Measurement of Submicron Fibers via Seeded Four-Wave-Mixing - Hammer, Jonas; Haupl, Daniel R.; Russell, Philip St. John; Joly, Nicolas (Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 2020)
We report non-destructive measurement of the diameter of submicron air-clad waveguides to nanometer precision, based on parametric amplification of a broadband seed signal. Ultrashort pump and seed pulses allow the diameter to be longitudinally resolved.
CRIS-Team Scopus Importer:2020-10-09

Nano-Optics in 2020 ± 20 - Sandoghdar, Vahid (Nano Letters, 2020)
CRIS-Team Scopus Importer:2020-07-31

Nanoscale Conducting Oxide PlasMOStor - Lee, Ho W.; Papadakis, Georgia; Burgos, Stanley P.; Chander, Krishnan; Kriesch, Arian; Pala, Ragip; Peschel, Ulf; Atwater, Harry A. (Nano Letters, 2014)
We experimentally demonstrate an ultracompact PlasMOStor, a plasmon slot waveguide field-effect modulator based on a transparent conducting oxide active region. By electrically modulating the conducting oxide material deposited into the gaps of highly confined plasmonic slot waveguides, we demonstrate field-effect dynamics giving rise to modulation with high dynamic range (2.71 dB/ extgreekmm) and low waveguide loss (∼0.45 dB/ extgreekmm). The large modulation strength is due to the large change in complex dielectric function when the signal wavelength approaches the surface plasmon resonance in the voltage-tuned conducting oxide accumulation layer. The results provide insight about the design of ultracompact, nanoscale modulators for future integrated nanophotonic circuits.
EAM Import::2019-03-12

Nanoscale spontaneous parametric down-conversion - Chekhova, Maria (Optics InfoBase Conference Papers, 2021)
We generate entangled photons via spontaneous parametric down-conversion (SPDC) in subwavelength films of nonlinear materials and all-dielectric nonlinear metasurfaces. The SPDC spectra reveal resonances: Fabry-Perot in the first case and Mie in the second case.
CRIS-Team Scopus Importer:2021-12-03

Nanoscopic Charge Fluctuations in a Gallium Phosphide Waveguide Measured by Single Molecules - Shkarin, Alexey; Rattenbacher, Dominik; Renger, Jan; Hönl, Simon; Utikal, Tobias; Seidler, Paul; Götzinger, Stephan; Sandoghdar, Vahid (Physical Review Letters, 2021)
We present efficient evanescent coupling of single organic molecules to a gallium phosphide (GaP) subwavelength waveguide (nanoguide) decorated with microelectrodes. By monitoring their Stark shifts, we reveal that the coupled molecules experience fluctuating electric fields. We analyze the spectral dynamics of different molecules over a large range of optical powers in the nanoguide to show that these fluctuations are light-induced and local. A simple model is developed to explain our observations based on the optical activation of charges at an estimated mean density of 2.5×1022 m-3 in the GaP nanostructure. Our work showcases the potential of organic molecules as nanoscopic sensors of the electric charge as well as the use of GaP nanostructures for integrated quantum photonics.
CRIS-Team Scopus Importer:2021-04-30

Nanostructured Alkali-Metal Vapor Cells - Cutler, T. F.; Hamlyn, W. J.; Renger, J.; Whittaker, K. A.; Pizzey, D.; Hughes, I. G.; Sandoghdar, Vahid; Adams, C. S. (Physical Review Applied, 2020)
Atom-light interactions in micro- and nanoscale systems hold great promise for alternative technologies based on integrated emitters and optical modes. We present the design architecture, construction method, and characterization of an all-glass alkali-metal vapor cell with nanometer-scale internal structure. Our cell has a glue-free design that allows versatile optical access, in particular with high numerical aperture optics, and incorporates a compact integrated heating system in the form of an external deposited indium tin oxide layer. By performing spectroscopy in different illumination and detection schemes, we investigate atomic densities and velocity distributions in various nanoscopic landscapes. We apply a two-photon excitation scheme to atoms confined in one dimension within our cells, achieving resonance line widths more than an order of magnitude smaller than the Doppler width. We also demonstrate sub-Doppler line widths for atoms confined in two dimensions to micron-sized channels. Furthermore, we illustrate control over vapor density within our cells through nanoscale confinement alone, which could offer a scalable route towards room-temperature devices with single atoms within an interaction volume. Our design offers a robust platform for miniaturized devices that could easily be combined with integrated photonic circuits.
CRIS-Team WoS Importer:2020-10-23

Narrowband Vacuum Ultraviolet Light via Cooperative Raman Scattering in Dual-Pumped Gas-Filled Photonic Crystal Fiber - Tyumenev, Rinat; Russell, Philip St. John; Novoa, David (ACS Photonics, 2020)
Many fields such as biospectroscopy and photochemistry often require sources of vacuum ultraviolet (VUV) pulses featuring a narrow line width and tunable over a wide frequency range. However, the majority of available VUV light sources do not simultaneously fulfill those two requirements and few if any are truly compact, cost-effective, and easy to use by nonspecialists. Here we introduce a novel approach that goes a long way to meeting this challenge. It is based on hydrogen-filled hollow-core photonic crystal fiber pumped simultaneously by two spectrally distant pulses. Stimulated Raman scattering enables the generation of coherence waves of collective molecular motion in the gas, which together with careful dispersion engineering and control over the modal content of the pump light, facilitates cooperation between the two separate Raman combs, resulting in a spectrum that reaches deep into the VUV. Using this system, we demonstrate the generation of a dual Raman comb of narrowband lines extending down to 141 nm using only 100 mW of input power delivered by a commercial solid-state laser. The approach may enable access to tunable VUV light to any laboratory and therefore boost progress in many research areas across multiple disciplines.
CRIS-Team WoS Importer:2020-09-11

Narrowband VUV light by molecular modulation in dual-pumped H2-filled hollow-core photonic crystal fiber - Tyumenev, Rinat; Novoa, David; Russell, Philip St. John (Optics InfoBase Conference Papers, 2020)
A Raman comb extending down to 140 nm in the vacuum UV is generated in hydrogen-filled hollow-core photonic crystal fiber pumped simultaneously by visible and UV pulses obtained from a compact 1030 nm pump laser.
CRIS-Team Scopus Importer:2020-11-13

Naturally phase-matched second-harmonic generation in a whispering-gallery-mode resonator - Fuerst, J. U.; Strekalov, D. V.; Elser, Dominique Alexander; Lassen, M.; Andersen, U. L.; Marquardt, Christoph; Leuchs, Gerd (Physical Review Letters, 2010)
We demonstrate for the first time natural phase matching for optical frequency doubling in a high-Q whispering-gallery-mode resonator made of lithium niobate. A conversion efficiency of 9% is achieved at 30μW in-coupled continuous wave pump power. The observed saturation pump power of 3.2 mW is almost 2 orders of magnitude lower than the state-of-the-art value. This suggests an application of our frequency doubler as a source of nonclassical light requiring only a low-power pump, which easily can be quantum noise limited. Our theoretical analysis of the three-wave mixing in a whispering-gallery-mode resonator provides the relative conversion efficiencies for frequency doubling in various modes. © 2010 The American Physical Society.
CRIS-Team Scopus Importer:2022-06-05

Naturally phase matched second harmonic generation in a whispering gallery mode resonator - Fürst, Josef; Strekalov, Dmitry; Elser, Dominique Alexander; Lassen, Mikael; Andersen, Ulrik L.; Marquardt, Christoph; Leuchs, Gerd (Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010, 2010)
We observed conversion efficiencies of 9% at 30 μW pump power in LiNbO3, as well as self-limiting effects at high powers. The continuous-wave pump at a wavelength of 1064nm and the second-harmonic feature Q > 107. © 2010 Optical Society of America.
CRIS-Team Scopus Importer:2022-06-05

Near-Field Analysis of Bright and Dark Modes on Plasmonic Metasurfaces Showing Extraordinary Suppressed Transmission - Dobmann, Sabine; Kriesch, Arian; Ploss, Daniel; Peschel, Ulf (Advanced Optical Materials, 2014)
Plasmonic metasurfaces are investigated that consist of a sub-wavelength line pattern in an ultrathin ( 10 nm) silver film, designed for extraordinary suppressed transmission (EOST) in the visible spectral range. Measurements with a near-field scanning optical microscope (NSOM) demonstrate that farfield irradiation resonantly excites antenna-like (bright) modes that are localized on the metal ridges. The re-radiation of these modes into the far-field interferes destructively with the transmitted wave, thus suppressing transmission almost completely. In contrast, a second type of mode, bound (dark) surface plasmon polaritons (SPPs) launched from an NSOM tip, propagates well across the metasurface, preferentially perpendicular to the grating lines.
EAM Import::2019-03-12

Near-infrared single-photon spectroscopy of a whispering gallery mode resonator using energy-resolving transition edge sensors - Foertsch, Michael; Gerrits, Thomas; Stevens, Martin J.; Strekalov, Dmitry; Schunk, Gerhard; Fuerst, Josef U.; Vogl, Ulrich; Sedlmeir, Florian; Schwefel, Harald G. L.; Leuchs, Gerd; Nam, Sae Woo; Marquardt, Christoph (Journal of Optics, 2015)
We demonstrate a method to perform spectroscopy of near-infrared single photons without the need of dispersive elements. This method is based on a photon energy resolving transition edge sensor and is applied for the characterization of widely wavelength tunable narrow-band single photons emitted from a crystalline whispering gallery mode resonator. We measure the emission wavelength of the generated signal and idler photons with an uncertainty of up to 2 nm.
CRIS-Team Scopus Importer:2022-06-05
Keywords: boronitrene; graphene; nonlinear optics; sum-frequency generation

Neue Ergebnisse in der optischen Datengewinnung und der Weiterverarbeitung - Häusler, Gerd; et al. (Optische 3D-Formerfassung, 1999)
UnivIS-Import:2015-04-16:Pub.1999.nat.dphy.optik.1optik.neueer

New concept of a polymer optical ray splitter simulated by Raytracing with a new Bisection-Algorithm - Backhaus, Carsten; Dötzer, Florian; Hoffmann, Gerd-Albert; Lorenz, Lukas; Overmeyer, Ludger; Bock, Karlheinz; Lindlein, Norbert (Frontiers in Optics + Laser Science APS/DLS, 2019)
Recent fabrication methods print polymer optical waveguides (POWs) on three-dimensional carriers. The special geometry of the POWs enables the realisation of an optical ray splitter which is simulated by raytracing using a new bisection-algorithm.
Keywords: Laser light; Optical design; Polymer waveguides; Printed circuit boards; Ray tracing; Stray light

New insights into colloidal gold flakes: structural investigation, micro-ellipsometry and thinning procedure towards ultrathin monocrystalline layers - Hoffmann, B.; Bashouti, M. Y.; Feichtner, Thorsten; Mackovic, Mirza; Dieker, Christel; Salaheldin, A. M.; Richter, P.; Gordan, O. D.; Zahn, D. R. T.; Spiecker, Erdmann; Christiansen, S.; Hoffmann, Björn (Nanoscale, 2016)
High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, presumably single-crystalline gold flakes due to their superior materials properties. However, important details about their intrinsic structure and their optical properties are not well understood yet. In this study, we present a synthesis routine for large flakes with diameters of up to 70 mu m and an in-depth investigation of their structural and optical properties. The flakes are precisely analyzed by transmission electron microscopy, electron backscatter diffraction and micro-ellipsometry. We found new evidence for the existence of twins extending parallel to the Au flake 111 surfaces which have been found to not interfere with the presented nanopatterning. Micro-Ellipsometry was carried out to determine the complex dielectric function and to compare it to previous measurements of bulk single crystalline gold. Finally, we used focused ion beam milling to prepare smooth crystalline layers and high-quality nanostructures with desired thickness down to 10 nm to demonstrate the outstanding properties of the flakes. Our findings support the plasmonics and nano optics community with a better understanding of this material which is ideally suited for superior plasmonic nanostructures.

New Modifications of the Coherence Radar - Häusler, Gerd; et al. (Proc. of the 3rd Int. Workshop on Automatic Processing of Fringe Patterns, 1997)
UnivIS-Import:2015-04-16:Pub.1997.nat.dphy.optik.1optik.newmod

New Range Sensors at the Physical Limit of Measuring Uncertainty - Häusler, Gerd; et al. (Proc. of the EOS Topical Meeting on Optoelectronics Distance Measurements and Applications, 1997)
UnivIS-Import:2015-04-16:Pub.1997.nat.dphy.optik.1optik.newran

Noise-free QND-measurement using optical solitons - Leuchs, Gerd; et al. (Physical Review A, 1998)
UnivIS-Import:2015-03-05:Pub.1998.nat.dphy.optik.1optik.noisef

Noise-powered probabilistic concentration of phase information - Usuga, Mario A.; Müller, Christian; Wittmann, Christoffer; Marek, Petr; Filip, Radim; Marquardt, Christoph; Leuchs, Gerd; Andersen, Ulrik L. (Nature Physics, 2010)
Phase-insensitive optical amplification of an unknown quantum state is known to be a fundamentally noisy operation that inevitably adds noise to the amplified state. However, this fundamental noise penalty in amplification can be circumvented by resorting to a probabilistic scheme as recently proposed and demonstrated in refs 6, 7, 8. These amplifiers are based on highly non-classical resources in a complex interferometer. Here we demonstrate a probabilistic quantum amplifier beating the fundamental quantum limit using a thermal-noise source and a photon-number-subtraction scheme. The experiment shows, surprisingly, that the addition of incoherent noise leads to a noiselessly amplified output state with a phase uncertainty below the uncertainty of the state before amplification. This amplifier might become a valuable quantum tool in future quantum metrological schemes and quantum communication protocols. © 2010 Macmillan Publishers Limited. All rights reserved.
CRIS-Team Scopus Importer:2022-06-05

NOLM based DPSK Signal Regeneration - Striegler, Arne; Meißner, Markus; Cvecek, Kristian; Sponsel, Klaus; Leuchs, Gerd; Schmauß, Bernhard (IEEE Photonics Technology Letters, 2005)
We present a nonlinear optical loop mirror (NOLM)-based 2R-regenerator setup, which is capable of regenerating signals modulated in phase-sensitive modulation formats. In a conventional NOLM, fluctuations of the signal amplitude are converted into phase fluctuations. Therefore, it is not suitable for regeneration of signals, modulated in formats such as differential phase-shift keying (DPSK) or duobinary. In this letter, we present a modified NOLM setup for 2R-regeneration taking return-to-zero DPSK as an example. © 2005 IEEE.
UnivIS-Import:2015-03-09:Pub.2005.nat.dphy.optik.1optik.nolmba
Keywords: All-optical regeneration; Differential phase-shift keying (DPSK); Nonlinear optical loop mirror (NOLM)

Non-classical light generated in a whispering gallery mode parametric oscillator - Förtsch, Michael; Schunk, G.; Fürst, J. U.; Strekalov, D. V.; Aiello, A.; Andersen, U. L.; Marquardt, Christoph; Leuchs, Gerd (Optics InfoBase Conference Papers, 2011)
We present the generation of quantum correlated twin beams in a whispering gallery mode resonator made from lithium niobate and the first direct observation of amplitude squeezing for the single parametric beams. © 2011 AOS.
CRIS-Team Scopus Importer:2022-06-05

Noninvasive manipulation of the optical response of opal photonic crystals - Romanov, Sergei G.; Regensburger, Alois; Korovin, Alexander V.; Romanova, Alexandra; Peschel, Ulf (Physical Review B, 2013)
The efficient manipulation with optical spectra of colloidal photonic crystals was achieved using the metal mirror positioned either immediately or at a distance from the crystal surface. If the mirror is close to the surface, the changes are mostly quantitative and relate to the improved light confinement. If the spacer provides a 2 extgreekp phase shift for round trip of the light at the wavelength of the diffraction resonance of the opal lattice, the defect band is formed in the photonic stop-band leading to 20–40 times increase of the transmission. The upper limit of the quality factor of the defect band was estimated by extrapolating the development of the defect transmission band as a function of the photonic crystal thickness. The specific features related to the photonic crystal dimensionality were revealed in the defect band spectra. The obtained results support the idea of achieving the control on the optical functionality of photonic crystals by recycling the transmitted light in the crystal volume.
EAM Import::2019-03-08

Non-invasive real-time characterization of hollow-core photonic crystal fibers using whispering gallery mode spectroscopy - Frosz, Michael H.; Pennetta, Riccardo; Enders, Michael T.; Ahmed, Goran; Russell, Philip St. John (Optics Express, 2019)
Single-ring hollow-core photonic crystal fibers, consisting of a ring of one or two thin-walled glass capillaries surrounding a central hollow core, hold great promise for use in optical communications and beam delivery, and are already being successfully exploited for extreme pulse compression and efficient wavelength conversion in gases. However, achieving low loss over long (km) lengths requires highly accurate maintenance of the microstructure—a major fabrication challenge. In certain applications, for example adiabatic mode transformers, it is advantageous to taper the fibers, but no technique exists for measuring the delicate and complex microstructure without first cleaving the taper at several positions along its length. In this Letter, we present a simple non-destructive optical method for measuring the diameter of individual capillaries. Based on recording the spectrum scattered from whispering gallery modes excited in the capillary walls, the technique is highly robust, allowing real-time measurement of fiber structure during the draw with sub-micron accuracy.
CRIS-Team Scopus Importer:2019-10-29

Non-invasive real-time characterization of hollow-core photonic crystal fibres using whispering gallery mode spectroscopy - Frosz, Michael H.; Pennetta, Riccardo; Enders, Michael T.; Ahmed, Goran; Russell, Philip St. John (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
Single-ring hollow-core photonic crystal fibre (SR-PCF), consisting of a ring of thin-walled glass capillaries surrounding a central hollow core, can offer remarkably low transmission loss [1], and is finding applications in, e.g., wavelength conversion and pulse compression in gases, high-power beam delivery and circular dichroism [2]. As with all microstructured fibres, it is highly desirable to continuously measure the internal structural parameters (e.g. the capillary diameter) during fibre drawing. This would improve the yield of useful fibre lengths, as well as offering better control of structural uniformity along the fibre. Successful tapering of hollow-core fibres also requires a non-destructive method of verifying structural integrity along the taper.
CRIS-Team Scopus Importer:2019-11-15

Nonlinear and quantum optics with whispering gallery resonators - Strekalov, Dmitry V.; Marquardt, Christoph; Matsko, Andrey B.; Schwefel, Harald G. L.; Leuchs, Gerd (Journal of Optics, 2016)
Optical whispering gallery modes (WGMs) derive their name from a famous acoustic phenomenon of guiding a wave by a curved boundary observed nearly a century ago. This phenomenon has a rather general nature, equally applicable to sound and all other waves. It enables resonators of unique properties attractive both in science and engineering. Very high quality factors of optical WGM resonators persisting in a wide wavelength range spanning from radio frequencies to ultraviolet light, their small mode volume, and tunable in- and out- coupling make them exceptionally efficient for nonlinear optical applications. Nonlinear optics facilitates interaction of photons with each other and with other physical systems, and is of prime importance in quantum optics. In this paper we review numerous applications of WGM resonators in nonlinear and quantum optics. We outline the current areas of interest, summarize progress, highlight difficulties, and discuss possible future development trends in these areas.
CRIS-Team Scopus Importer:2022-06-05
Keywords: microresonators; non-classical light; optical wave mixing

Nonlinear enhanced microresonator gyroscope - Silver, Jonathan M.; Del Bino, Leonardo; Woodley, Michael T. M.; Ghalanos, George N.; Svela, Andreas O.; Moroney, Niall; Zhang, Shuangyou; Grattan, Kenneth T.; Del'Haye, Pascal (Optica, 2021)
Optical gyroscopes based on the Sagnac effect have been the mainstay of inertial navigation in aerospace and shipping for decades. These gyroscopes are typically realized either as ring-laser gyroscopes (RLGs) or fiber-optic gyroscopes (FOGs). With the recent rapid progress in the field of ultrahigh-quality optical whispering-gallery mode and ring microresonators, attention has been focused on the development of microresonator-based Sagnac gyroscopes as a more compact alternative to RLGs and FOGs. One avenue that has been explored is the use of exceptional points in non-Hermitian systems to enhance the responsivity to rotation. We use a similar phenomenon, namely, the critical point of a spontaneous symmetry-breaking transition between counterpropagating light, to demonstrate a microresonator gyroscope with a responsivity enhanced by a factor of around 10(4). We present a proof-of-principle rotation measurement as well as a characterization of the system's dynamical response, which shows the universal critical behaviors of responsivity enhancement and critical slowing down, both of which are beneficial in an optical gyroscope. We believe that this concept could be used to realize simple and cheap chip-based gyroscopes with sensitivities approaching those of today's RLGs and FOGs. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
CRIS-Team WoS Importer:2021-10-08

Nonlinear optics in crystalline: Whispering gallery resonators - Marquardt, Christoph; Strekalov, Dmitry V.; Fürst, Josef; Förtsch, Michael; Leuchs, Gerd (Optics and Photonics News, 2013)
CRIS-Team Scopus Importer:2022-06-05

Nonlinear optics with full three-dimensional illumination - Penjweini, Rojiar; Weber, Markus; Sondermann, Markus; Boyd, Robert W.; Leuchs, Gerd (Optica, 2019)

Nonlinear optics with one molecule and two photons - Pscherer, Andre; Meierhofer, Manuel; Wang, Daqing; Kelkar, Hrishikesh; Martin-Cano, DIego; Utikal, Tobias; Gotzinger, Stephan; Sandoghdar, Vahid (2021 Conference on Lasers and Electro-Optics, CLEO 2021 - Proceedings, 2021)
We use single solid state organic molecules strongly coupled to a tunable FabryPerot microcavity to perform nonlinear optics experiments at the single quantum limit.
CRIS-Team Scopus Importer:2021-12-24

Nonlinear Phase Noise Compensation Using a Modified Nonlinear Optical Loop Mirror - Sponsel, K.; Stephan, C.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (OSA Optics and Photonics Congress, Advanced Photonics, BGPP Topical Meeting, Karlsruhe, 21.-24. Juni, 2010)
lhft_intern.bib::Sponsel10

Nonlinear Phase Noise Reduction in a DPSK Transmission System Using Cascaded Nonlinear Amplifying Loop Mirrors - Stephan, Christian; Sponsel, Klaus; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE Photonics Technology Letters, 2009)
The performance of a nonlinear amplifying loop mirror as a phase-preserving amplitude 2R regenerator in a differential phase-shift-keying transmission system with nonlinear phase noise as dominant limiting effect has been investigated in a recirculating fiber-loop setup. The experimental results show that cascaded regenerators can efficiently prevent the accumulation of nonlinear phase noise in such systems. It was possible to significantly increase the transmission quality; alternatively, a considerable increase of fiber launch power could be achieved for the same bitor ratio. As a limiting effect, the amplified Rayleigh backscattering in the highly nonlinear fiber is identified when the regenerator is passed multiple times. © 2009 IEEE.
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.optik.1optik.nonlin
Keywords: 2r regeneration; Differential phase-shift keying (DPSK); Nonlinear amplifying loop mirror (NALM); Nonlinear phase noise

Nonlinear Phase-Shift Compensation by a Nonlinear Amplifying Loop Mirror - Schmauß, Bernhard; Sponsel, Klaus; Stephan, C.; Onishchukov, Georgy; Leuchs, Gerd (Conference on Lasers and Electro-Optics CLEO, Paper JThE59, San Jose, May, 2010)
The nonlinear amplifying loop mirror as a nonlinear phase-shift compensator for multilevel phase-encoded optical signals is considered. Simulations of a 20 Gb/s DQPSK transmission system showed a significant BER improvement for post-compensation.
lhft_intern.bib::Schmauss10a

Nonlinear power dependence of the spectral properties of an optical parametric oscillator below threshold in the quantum regime - Shafiee, Golnoush; Strekalov, Dmitry; Otterpohl, Alexander; Sedlmeir, Florian; Schunk, Gerhard; Vogl, Ulrich; Schwefel, Harald G. L.; Leuchs, Gerd; Marquardt, Christoph (New Journal of Physics, 2020)
Photon pairs and heralded single photons, obtained from cavity-assisted parametric down conversion (PDC), play an important role in quantum communications and technology. This motivated a thorough study of the spectral and temporal properties of parametric light, both above the optical parametric oscillator (OPO) threshold, where the semiclassical approach is justified, and deeply below it, where the linear cavity approximation is applicable. The pursuit of a higher two-photon emission rate leads into an interesting intermediate regime, between above OPO threshold and very low pump power, where the OPO still operates considerably below the threshold but the nonlinear cavity phenomena cannot be neglected anymore. Here, we investigate this intermediate regime and show that the spectral and temporal properties of the photon pairs, as well as their emission rate, may significantly differ from the widely accepted linear model. The observed phenomena include frequency pulling and broadening in the temporal correlation for the down-converted optical fields. These factors need to be taken into account when devising practical applications of the high-rate cavity-assisted spontaneous PDC sources.
CRIS-Team WoS Importer:2020-08-21

Nonlinear Quantum Optics in a Millimeter Size Whispering Gallery Mode Resonator - Leuchs, Gerd; Marquardt, Christoph; Schwefel, Harald (Nonlinear Optics, NLO 2015, 2015)
Whispering gallery resonators made from nonlinear crystals offer high quality factors combined with small mode volumes leading to an enhanced effective X(2) nonlinearity. These properties facilitate studying quantum optical effects in the nonlinear regime with interacting fields differing in frequency by up to four orders of magnitude. Furthermore, the small size results in a large mode spacing allowing for heralded single photon generation in a single mode
CRIS-Team Scopus Importer:2022-06-05

Nonlinear single sideband microwave to optical conversion using an electro-optic WGM-resonator - 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. (Optics InfoBase Conference Papers, 2016)
Nonlinear electro-optical conversion of microwave radiation into the optical telecommunication band is achieved within a crystalline whispering gallery mode resonator, reaching 0.1% photon number conversion efficiency with MHz bandwidth.
CRIS-Team Scopus Importer:2021-06-29

Nonlocality from N > 2 independent single-photon emitters - Thiel, Christoph; Wiegner, Ralph; von Zanthier, Joachim; Agarwal, G. S. (Physical Review A, 2010)
We demonstrate that intensity correlations of second order in the fluorescence light of N > 2 single-photon emitters may violate locality while the visibility of the signal remains below 1/root 2 approximate to 71%. For this, we derive a homogeneous Bell-Wigner-type inequality, which can be applied to a broad class of experimental setups. We trace the violation of this inequality back to path entanglement created by the process of detectio

Non-null testing of aspherical surfaces by using a Shack-Hartmann sensor - Lindlein, Norbert; Pfund, Johannes; Schwider, Johannes (OSA Technical Digest, 2000)
UnivIS-Import:2015-04-16:Pub.2000.nat.dphy.optik.1optik.nonnul

Nonnull testing of rotationally symmetric aspheres: a systematic error assessment - Lindlein, Norbert; et al. (Applied Optics, 2001)
An optical setup for the testing of rotationally symmetric aspheres without a null optic is proposed. The optical setup is able to transfer the strongly curved wave fronts that stem from the reflection of a spherical testing wave front at a rotationally symmetric asphere. By simulation it is proved that the algorithms of the Shack-Hartmann sensor that is used can cope with the steep wave-front slopes (∼110λ/mm) in the detection plane. The systematic errors of the testing configuration are analyzed and separated. For all types of error, functionals are derived whose significance is proved by simulation. The maximum residual errors in the simulations are fewer than λ/500 (peak to valley). © 2001 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.optik.1optik.nonnul

Nonparaxial polarizers - Aiello, Andrea; Marquardt, Christoph; Leuchs, Gerd (Optics Letters, 2009)
We develop a theoretical description for polarizers that goes beyond the paraxial approximation. By combining existing theories for fields with nonplanar wavefronts, we are able to derive a simple power series expansion expressing the electric field of a light beam after a polarizer as a linear function of the field and its spatial derivatives evaluated before the polarizer. The first few terms of such expansion are explicitly given, and their physical meaning is discussed. © 2009 Optical Society of America.
CRIS-Team Scopus Importer:2022-06-05

Non-phase matched spontaneous parametric down conversion in ultra-thin lithium niobate - Okoth, Cameron; Santiago, Tomás; Cavanna, Andrea; Chekhova, Maria (Optics InfoBase Conference Papers, 2019)
We report the generation of entangled photon pairs via type-0 spontaneous parametric down conversion in ultra-thin lithium niobate in which momentum between the.
CRIS-Team Scopus Importer:2019-07-09

Nonreciprocal vortex isolator via topology-selective stimulated Brillouin scattering - Zeng, Xinglin; Russell, Philip St J.; Wolff, Christian; Frosz, Michael H.; Wong, Gordon K.L.; Stiller, Birgit (Science Advances, 2022)
Optical nonreciprocity, which breaks the symmetry between forward and backward propagating optical waves, has become vital in photonic systems and enables many key applications. So far, all the existing nonreciprocal systems are implemented for linearly or randomly polarized fundamental modes. Optical vortex modes, with wavefronts that spiral around the central axis of propagation, have been extensively studied over the past decades and offer an additional degree of freedom useful in many applications. Here, we report a light-driven nonreciprocal isolation system for optical vortex modes based on topology-selective stimulated Brillouin scattering (SBS) in chiral photonic crystal fiber. The device can be reconfigured as an amplifier or an isolator by adjusting the frequency of the control signal. The experimental results show vortex isolation of 22 decibels (dB), which is at the state of the art in fundamental mode isolators using SBS. This device may find applications in optical communications, fiber lasers, quantum information processing, and optical tweezers.
CRIS-Team Scopus Importer:2022-11-04

Nonunity gain minimal-disturbance measurement - Leuchs, Gerd; et al. (Physical Review A, 2007)
We propose and experimentally demonstrate an optimal nonunity gain Gaussian scheme for partial measurement of an unknown coherent state that causes minimal disturbance of the state. The information gain and the state disturbance are quantified by the noise added to the measurement outcomes and to the output state, respectively. We derive the optimal trade-off relation between the two noises and we show that the tradeoff is saturated by nonunity gain teleportation. Optimal partial measurement is demonstrated experimentally using a linear optics scheme with feedforward. © 2007 The American Physical Society.
UnivIS-Import:2015-03-09:Pub.2007.nat.dphy.optik.1optik.nonuni

Non-unity gain quantum nondemolition measurements based on measurement and re-preparation - Leuchs, Gerd; et al. (Optics Letters, 2006)
UnivIS-Import:2015-03-09:Pub.2006.nat.dphy.optik.1optik.nonuni

Novel diagnostic and therapeutic techniques reveal changed metabolic profiles in recurrent focal segmental glomerulosclerosis - Müller-Deile, Janina; Sarau, George; Kotb, Ahmed M.; Jaremenko, Christian; Rolle-Kampczyk, Ulrike E.; Daniel, Christoph; Kalkhof, Stefan; Christiansen, Silke H.; Schiffer, Mario (Scientific Reports, 2021)
Idiopathic forms of Focal Segmental Glomerulosclerosis (FSGS) are caused by circulating permeability factors, which can lead to early recurrence of FSGS and kidney failure after kidney transplantation. In the past three decades, many research endeavors were undertaken to identify these unknown factors. Even though some potential candidates have been recently discussed in the literature, “the” actual factor remains elusive. Therefore, there is an increased demand in FSGS research for the use of novel technologies that allow us to study FSGS from a yet unexplored angle. Here, we report the successful treatment of recurrent FSGS in a patient after living-related kidney transplantation by removal of circulating factors with CytoSorb apheresis. Interestingly, the classical published circulating factors were all in normal range in this patient but early disease recurrence in the transplant kidney and immediate response to CytoSorb apheresis were still suggestive for pathogenic circulating factors. To proof the functional effects of the patient’s serum on podocytes and the glomerular filtration barrier we used a podocyte cell culture model and a proteinuria model in zebrafish to detect pathogenic effects on the podocytes actin cytoskeleton inducing a functional phenotype and podocyte effacement. We then performed Raman spectroscopy in the < 50 kDa serum fraction, on cultured podocytes treated with the FSGS serum and in kidney biopsies of the same patient at the time of transplantation and at the time of disease recurrence. The analysis revealed changes in podocyte metabolome induced by the FSGS serum as well as in focal glomerular and parietal epithelial cell regions in the FSGS biopsy. Several altered Raman spectra were identified in the fractionated serum and metabolome analysis by mass spectrometry detected lipid profiles in the FSGS serum, which were supported by disturbances in the Raman spectra. Our novel innovative analysis reveals changed lipid metabolome profiles associated with idiopathic FSGS that might reflect a new subtype of the disease.
CRIS-Team Scopus Importer:2021-03-19

Novel sources for polarisation squeezing and polarisation entanglement using photonic crystal fibres - Milanovic, Josip; Lassen, Mikael; Förtsch, Michael; Marquardt, Christoph; Andersen, Ulrik Lund; Leuchs, Gerd (CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009)
CRIS-Team Scopus Importer:2022-06-05

Null-Test-Measurement of Cylindrical Microlenses in Transmitted Light - Lindlein, Norbert; et al. (VDI-Berichte, 2002)
A fiber optic Mach-Zehnder-interferometer is described, which allows the test of cylindrical microlenses with a high numerical aperture in transmitted light. The interferometer is working in the near infrared and uses diffractive optical elements as null lenses providing a reference cylindrical wave. The setup, the null-optic, the light source and a method to eliminate misalignment aberrations are described in detail and a typical measurement sequence is presented.
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.nullte

Null test measurement of high-numerical aperture cylindrical micro lenses in transmitted light - Lindlein, Norbert; et al. (Optical Manufacturing and Testing V, 2003)
An interferometrical measurement method is presented for determining the quality of cylindrical micro lenses with a numerical aperture of up to 0.8 in transmitted light. In order to maximize the achievable accuracy, a null test configuration was chosen. The reference cylindrical waves are shaped by computer generated diffractive optical elements (DOEs), which are made by optical or e-beam lithography. The resulting wave front is analyzed by a fiber optic phase-shifting Mach-Zehnder-interferometer or a Shack-Hartmann wave front sensor. Besides the general setup, which is working in the near infrared (NIR), special aspects will be presented concerning the elimination of misalignment aberrations, the complete filtering of parasitic diffraction orders and the generation of an anamorphic optical transformation for increasing the lateral resolution perpendicular to the cylindrical axis. By means of experimental results the possibilities and accuracy of this technique are discussed.
Keywords: Cylindrical micro lens; Diffractive optics; Null test; Phase shifting interferometry

Observation of Entanglement between a superconducting Qubit and an Itinerant Microwave Field - Eichler, Christopher (2012)
The generation of entanglement between stationary qubits and propagating photons both enables the study of non-local effects in quantum mechanics and provides a resource for communication between different nodes in a quantum network. Qubit - photon entanglement has so far only been implemented at optical frequencies with single atoms or electron spins. Recent progress in the development of superconducting qubits and in the characterization of propagating microwave fields has also enabled exciting new quantum optics experiments using microwaves. Here, we present experiments in which we prepare and reconstruct the state of non-classical microwave fields by combining novel photon field characterization methods with efficient measurement techniques. We also demonstrate the generation of entangled states between a superconducting qubit and a photon field. Extracting all relevant correlations between the two systems we are able to reconstruct the full density matrix and to verify the entanglement of Bell type states and more complex ones.
Keywords: wwwqudev

Observation of light propagation in volume scatterers with 10 11-fold slow motion - Häusler, Gerd; et al. (Optics Letters, 1996)
UnivIS-Import:2015-03-05:Pub.1996.nat.dphy.optik.1optik.observ

Observation of multimode quantum correlations in fiber optical solitons - Leuchs, Gerd; et al. (Physical Review Letters, 1998)
Quantum correlations of photon numbers in different spectral components of ultrashort optical solitons have been observed experimentally. These correlations are crucial for the understanding and characterization of the internal quantum structure of soliton pulses and contribute significantly to soliton squeezing by spectral filtering. The accessible information on the nonclassical state of the correlated spectral components is discussed with the example of two modes. The method may be generalized to obtain a complete quantum description of a multimode field.
UnivIS-Import:2015-03-05:Pub.1998.nat.dphy.optik.1optik.observ

Observation of the Geometric Spin Hall Effect of Light - Korger, Jan; Aiello, Andrea; Chille, Vanessa; Wittmann, Christoffer; Lindlein, Norbert; Marquardt, Christoph; Leuchs, Gerd (Physical Review Letters, 2014)

Observation of Time Reversed Light Propagation by an Exchange of Eigenstates - Wimmer, Martin; Peschel, Ulf (Scientific Reports, 2018)
As time flow dictates all evolution, its effective reversal is a topic of active research in a broad range of disciplines, including acoustics, hydrodynamics and optics. This multifarious set of environments is reflected by a great diversity of approaches to observe various echoes of wave functions. Here, we experimentally demonstrate time reversal of a pulse sequence propagating through a photonic mesh lattice realized by two coupled loops of telecommunication fibres. Our system features a symmetric band structure, which allows for almost perfect reversal of its evolution by exchanging the population between two opposing bands. The protocol applied is based on a non-adiabatic and instantaneous exchange of eigenstates resulting in highly efficient time reversal of a pulse chain.
CRIS-Team Scopus Importer:2023-04-20

On-Demand Coupling of Electrically Generated Excitons with Surface Plasmons via Voltage-Controlled Emission Zone Position - Zakharko, Yuriy; Held, Martin; Sadafi, Fabrizio-Zagros; Gannott, Florentina; Mandavi, Ali; Peschel, Ulf; Klupp Taylor, Robin; Zaumseil, Jana (ACS Photonics, 2016)
The ability to confine and manipulate light below the diffraction limit is a major goal of future multifunctional optoelectronic/plasmonic systems. Here, we demonstrate the design and realization of a tunable and localized electrical source of excitons coupled to surface plasmons based on a polymer light emitting field-effect transistor (LEFET). Gold nanorods that are integrated into the channel support localized surface plasmons and serve as nanoantennas for enhanced electroluminescence. By precise spatial control of the near-infrared emission zone in the LEFET via the applied voltages the near-field coupling between electrically generated excitons and the nanorods can be turned on or off as visualized by a change of electroluminescence intensity. Numerical calculations and spectroscopic measurements corroborate significant local electroluminescence enhancement due to the high local density of photonic states in the vicinity of the gold nanorods. Importantly, the integration of plasmonic nanostructures hardly influences the electrical performance of the LEFETs, thus, highlighting their mutual compatibility in novel active plasmonic devices.
Keywords: surface plasmon polariton; organic semiconductor; field-effect transistor; electroluminescence; Purcell effect; active plasmonics

Online Monitoring of Microscale Liquid-Phase Catalysis Using in-Fiber Raman Spectroscopy - Schorn, Florian; Aubermann, Manfred; Zeltner, Richard; Haumann, Marco; Joly, Nicolas (ACS Catalysis, 2021)
We report on the use of hollow-core photonic crystal fibers to monitor the evolution of chemical reactions. The combination of tight confinement and long interaction length allows single-pass spectroscopic measurements using less than a microliter volume of chemicals with good accuracy. As a proof of principle, we used here nonlinear Raman spectroscopy for a reaction screening of the acidic catalyzed esterification of methanol and acetic acid.
CRIS-Team Scopus Importer:2021-07-02
Keywords: esterification; hollow-core photonic crystal fibers; in situ spectroscopy; microreactor; Raman

On Quantum Efficiency Measurements and Plasmonic Antennas - Matsuzaki, Korenobu; Liu, Hsuan Wei; Götzinger, Stephan; Sandoghdar, Vahid (ACS Photonics, 2021)
Quantum efficiency is a key quantity that describes the performance of light-emitting materials and is, thus, an important metric for assessing novel nanophotonic systems. This Perspective provides a concise discussion of the difficulties encountered in the characterization of quantum efficiencies, especially for studies that involve single emitters. In particular, we review various approaches that have been recently used for determining quantum efficiencies of emitters coupled to plasmonic antennas and highlight the subtleties and challenges that hinder precise measurements.
CRIS-Team Scopus Importer:2021-06-25
Keywords: antenna; plasmonic; Purcell enhancement; quantum efficiency; quenching; spontaneous emission

On the analogy between a single atom and an optical resonator - Heugel, Simon Tobias; Villar, Alessandro; Sondermann, Markus; Peschel, Ulf; Leuchs, Gerd (Laser Physics, 2010)
A single atom in free space can have a strong influence on a light beam and a single photon can have a strong effect on a single atom in free space. Regarding this interaction, two conceptually different questions can be asked: can a single atom fully absorb a single photon and can a single atom fully reflect a light beam. The conditions for achieving the full effect in either case are different. Here we discuss related questions in the context of an optical resonator. When shaping a laser pulse properly it will be fully absorbed by an optical resonator, i.e., no light will be reflected and all the pulse energy will accumulate inside the resonator before it starts leaking out. We show in detail that in this case the temporal pulse shape has to match the time-reversed pulse obtained by the cavity's free decay. On the other hand a resonator, made of highly reflecting mirrors which normally reflect a large portion of any incident light, may fully transmit the light, as long as the light is narrow band and resonant with the cavity. The analogy is the single atom-normally letting most of the light pass-which under special conditions may fully reflect the incident light beam. Using this analogy we are able to study the effects of practical experimental limitations in the atom-photon coupling, such as finite pulses, bandwidths, and solid angle coverage, and to use the optical resonator as a test bed for the implementation of the quantum experiment. © 2010 Pleiades Publishing, Ltd.

On the experimental investigation of the electric and magnetic response of a single nano-structure - Banzer, Peter; Peschel, Ulf; Quabis, Susanne; Leuchs, Gerd (Optics Express, 2010)
We demonstrate an experimental method to separately test the optical response of a single sub-wavelength nano-structure to tailored electric and magnetic field distributions in the optical domain. For this purpose a highly focused y-polarized TEM10-mode is used which exhibits spatially separated longitudinal magnetic and transverse electric field patterns. By displacing a single sub-wavelength nano-structure, namely a single split-ring resonator (SRR), in the focal plane, different coupling scenarios can be achieved. It is shown experimentally that the single split-ring resonator tested here responds dominantly as an electric dipole. A much smaller but yet statistically significant magnetic dipole contribution is also measured by investigating the interaction of a single SRR with a magnetic field component perpendicular to the SRR plane (which is equivalent to the curl of the electric field) as well as by analyzing the intensity and polarization distribution of the scattered light with high spatial resolution. The developed experimental setup as well as the measurement techniques presented in this paper are a versatile tool to investigate the optical properties of single sub-wavelength nano-structures.
EAM Import::2019-03-08

On-the-fly particle metrology in hollow-core photonic crystal fibre - Sharma, Abhinav; Xie, Shangran; Zeltner, Richard; Russell, Philip St. John (Optics Express, 2019)
Efficient monitoring of airborne particulate matter (PM), especially particles with aerodynamic diameter less than 2.5 µm (PM2.5), is crucial for improving public health. Reliable information on the concentration, size distribution and chemical characteristics of PMs is key to evaluating air pollution and identifying its sources. Standard methods for PM2.5 characterization require sample collection from the atmosphere and post-analysis using sophisticated equipment in a laboratory environment, and are normally very time-consuming. Although optical methods based on analysis of scattering of free-space laser beams or evanescent fields are in principle suitable for real-time particle counting and sizing, lack of knowledge of the refractive index in these methods not only leads to inevitable sizing ambiguity but also prevents identification of the particle material. In the case of evanescent wave detection, the system lifetime is strongly limited by adhesion of particles to the surfaces. Here we report a novel technique for airborne particle metrology based on hollow-core photonic crystal fibre. It offers in situ particle counting, sizing and refractive index measurement with effectively unlimited device lifetime, and relies on optical forces that automatically capture airborne particles in front of the hollow core and propel them into the fibre. The resulting transmission drop, together with the time-of-flight of the particles passing through the fibre, provide unambiguous mapping of particle size and refractive index with high accuracy. The technique offers unique advantages over currently available real-time particle metrology systems, and can be directly applied to monitoring air pollution in the open atmosphere as well as precise particle characterization in a local environment such as a closed room or a reaction vessel.
CRIS-Team Scopus Importer:2019-12-10

Operational Determination of Multiqubit Entanglement Classes via Tuning of Local Operations - Bastin, T.; Thiel, Christoph; von Zanthier, Joachim; Lamata, Lucas; Solano, E.; Agarwal, G. S. (Physical Review Letters, 2009)
We present a physical setup with which it is possible to produce arbitrary symmetric long-lived multiqubit entangled states in the internal ground levels of photon emitters, including the paradigmatic Greenberger-Horne-Zeilinger and W states. In the case of three emitters, where each tripartite entangled state belongs to one of two well-defined entanglement classes, we prove a one-to-one correspondence between well-defined sets of experimental parameters, i.e., locally tunable polarizer orientations, and multiqubit entanglement classes inside the symmetric subspac

Opportunities and challenges of single protein detection with iSCAT - Nicoli, Francesca; König, Katharina; Dahmardeh, Mahyar; Gemeinhardt, André; Mahmoodabadi, Reza Gholami; Mirzaalian Dastjerdi, Houman; Köstler, Harald; Sandoghdar, Vahid (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, 2019)
In recent decades large efforts have been made to push optical imaging to the limit, for example for detecting very small proteins. Great achievements have been obtained with fluorescence microscopy, both in terms of localization precision and study of the dynamics of different molecules. Despite the constant improvements, fluorescence-based methods suffer from intrinsic limitations, such as the finite number of emitted photons and photo damage, which limits the temporal resolution and the duration of a measurement. Furthermore, if the molecule of interest is intrinsically non-fluorescent, it has to be labelled with a suitable fluorophore, which in case of biological molecules could interfere with their activity and behavior.
CRIS-Team Scopus Importer:2019-11-15

Optical 3D Sensors - Häusler, Gerd (Principles of 3D Image Analysis and Synthesis, 2000)
UnivIS-Import:2015-04-20:Pub.2000.nat.dphy.optik.1optik.optica_0

Optical amplification at the quantum limit - Andersen, Ulrik Lund; Leuchs, Gerd (Journal of Modern Optics, 2007)
In this paper we evaluate experimentally measured signal-to-noise ratio performance of different types of optical amplifiers [V. Josse, M. Sabuncu, N. Cerf, et al., Phys. Rev. Lett. 96 163602 (2006); Z.Y. Ou, S.F. Pereira and H.J. Kimble, Phys. Rev. Lett. 70 3239 (1993)]. We pay particular attention to the low gain regime where the quantum limit of the amplifier varies with gain. Independent of the amplifier type the noise performance is remarkably close to the quantum limit. Low gain optical amplifiers are of interest for quantum communication.
UnivIS-Import:2015-03-09:Pub.2007.nat.dphy.optik.1optik.optica

Optical Beam Propagation and Ray Tracing Simulation of Interruption-Free Asymmetric Multimode Bus Couplers - Lorenz, Lukas; Nieweglowski, Krzysztof; Wolter, Klaus-Jürgen; Loosen, Florian; Lindlein, Norbert; Bock, Karlheinz (Journal of Microelectronics and Electronic Packaging, 2017)
In this article, we present a coupling concept for an interruption-free asymmetric bidirectional optical bus coupler for board and module level. With this approach, it is possible to connect several electro-optical devices to a single waveguide. A core-to-core connection principle is used, where the cores get into physical contact at their side faces. The coupling ratio can be tuned by adjusting the overlap area of the two cores with different contact pressures. Because of a bending in one of the waveguides, it is possible to achieve a specific asymmetric coupler design, where the coupling ratio depends on the coupling direction (bent waveguide to rigid one or vice versa). To derive design rules for prototyping, a simulation is performed using two different independent approaches for cross-checking. With a ray tracing simulation, coupling ratios and energy distribution within the bent core are analyzed. In addition, a simulation with the beam propagation method is used to take wave optical effects into account as well as to establish a holistic view on the coupling concept.
Keywords: Optical bus coupler; asymmetric coupling; planar multimode waveguide; beam propagation method; nonsequential ray tracing

Optical Coherence Profilometry (OCP) of human skin in vivo - Häusler, Gerd; et al. (SPIE j, 1997)
UnivIS-Import:2015-03-05:Pub.1997.nat.dphy.optik.1optik.multic

Optical Coherence Tomography by 'spectral radar': dynamic range estimation and in vivo measurements of skin - Häusler, Gerd; et al. (Proceedings of SPIE, 1998)
UnivIS-Import:2015-03-05:Pub.1998.nat.dphy.optik.1optik.optica

Optical Coherence Tomography by "Spectral Radar": Improvement of Signal-to-Noise Ratio - Häusler, Gerd; et al. (Proceedings of SPIE, 2000)
`Spectral radar' combines a white light interferometer with a spectrometer. It is an optical sensor for the acquisition of skin morphology based on OCT techniques. The scattering amplitude along one vertical axis from the surface into the bulk can be measured within one exposure. We will discuss some essentials of signal formation and a new method of signal evaluation that significantly reduces artifacts from some source imperfections. We will further demonstrate new measurements.
UnivIS-Import:2015-03-09:Pub.2000.nat.dphy.optik.1optik.optica_4

Optical coherence tomography with a nonlinear interferometer in the high parametric gain regime - MacHado, Gerard J.; Frascella, Gaetano; Torres, Juan P.; Chekhova, Maria (Applied Physics Letters, 2020)
We demonstrate optical coherence tomography based on an SU(1,1) nonlinear interferometer with high-gain parametric downconversion. For imaging and sensing applications, this scheme promises to outperform previous experiments working at low parametric gain, since higher photon fluxes provide lower integration times for obtaining high-quality images. In this way, one can avoid using single-photon detectors or CCD cameras with very high sensitivities, and standard spectrometers can be used instead. Other advantages are higher sensitivity to small loss and amplification before detection so that the detected light power considerably exceeds the probing one.
CRIS-Team Scopus Importer:2020-09-25

Optical coherence tomography with the Spectral Radar. Fast optical analysis in volume scatterers by short coherence interferometry - Häusler, Gerd; et al. (SPIE j, 1996)
We present a sensor for acquisition of cross-sectional images of volume scatterers, we call it 'spectral radar'. Medical and technical applications are possible. The sensor is a modified Michelson interferometer, with a broad bandwidth light source. The scattering amplitude a(z) along one vertical axis from the surface into the bulk can be measured within one exposure. No reference arm scanning is necessary. Measurement results of stationary and non stationary scattering phantoms, human skin and of a fish eye in vitro are show
UnivIS-Import:2015-03-05:Pub.1996.nat.dphy.optik.1optik.optica_3

Optical diametric drive acceleration through action–reaction symmetry breaking - Wimmer, Martin; Regensburger, Alois; Bersch, Christoph; Miri, Mohammad-Ali; Batz, Sascha; Onishchukov, Georgy; Christodoulides, Demetrios N.; Peschel, Ulf (Nature Physics, 2013)
Newton's third law of motion is one of the pillars of classical physics. This fundamental principle states that the forces two bodies exert on each other are equal and opposite. Had the resulting accelerations been oriented in the same direction, this would have instead led to a counterintuitive phenomenon, that of diametric drive. In such a hypothetical arrangement, two interacting particles constantly accelerate each other in the same direction through a violation of the action–reaction symmetry. Although in classical mechanics any realization of this process requires one of the two particles to have a negative mass and hence is strictly forbidden, it could nevertheless be feasible in periodic structures where the effective mass can also attain a negative sign. Here we report the first experimental observation of such diametric drive acceleration for pulses propagating in a nonlinear optical mesh lattice. The demonstrated reversal of action–reaction symmetry could enable altogether new possibilities for frequency conversion and pulse-steering applications.
EAM Import::2019-03-08

Optical Gap solitons and Truncated Nonlinear Bloch Waves in Temporal Lattices - Bersch, Christoph; Onishchukov, Georgy; Peschel, Ulf (Physical Review Letters, 2012)
We experimentally demonstrate the formation and stable propagation of various types of discrete temporal solitons in an optical fiber system. Pulses interacting with a time-periodic potential and defocusing nonlinearity are shown to form gap solitons and nonlinear truncated Bloch waves. Multi-pulse solitons with defects, as well as novel structures composed of a strong soliton riding on a weaker truncated nonlinear Bloch wave are shown to propagate over up to eleven coupling lengths. The nonlinear dynamics of all pulse structures is monitored over the full propagation distance which provides detailed insight into the soliton dynamics.
EAM Import::2019-03-08

Optical harmonic generation from bright squeezed vacuum - Spasibko, Kirill; Kopylov, Denis A.; Krutyanskiy, Victor L.; Murzina, Tatiana V.; Leuchs, Gerd; Chekhova, Maria (Optics InfoBase Conference Papers, 2017)
CRIS-Team Scopus Importer:2023-03-27

Optical Landau state mapping with in-plane electric fields - Karmakar, Biswajit; Schardt, Michael; Malzer, Stefan; Arora, Brij Mohan; Döhler, Gottfried (Physica Status Solidi (C) Current Topics in Solid State Physics, 2007)
We report on a theoretical and experimental investigation of magneto-absorption in quantum wells (QWs) in the presence of a uniform in-plane electric field. From a simple theoretical model a linear real-space shift of the electron Landau level wave functions relative to the hole counterparts is expected under increasing in-plane electric field. As a result, quadratic Stark shifts, fading of the zero-field allowed transitions, and increasing oscillator strength for the originally forbidden transitions are predicted. These predictions are confirmed by experiments on GaAs/AlGaAs-QWs and found to be in reasonably good agreement with simulations based on a simple model. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.

Optically addressable array of optomechanically compliant glass nanospikes on the endface of a soft-glass photonic crystal fiber - Wang, Zheqi; Xie, Shangran; Jiang, Xin; Babic, Fehim; Huang, Jiapeng; Pennetta, Riccardo; Köhler, Johannes; Russell, Philip St. John (ACS Photonics, 2019)
Arrays of elongated nanoscale structures with suitable optical and mechanical properties can act as probes of numerous physical processes at the nanoscale, with applications in for example high-resolution optical imaging and atomic force microscopy. They can also be used to investigate optomechanical phenomena such as synchronization among large assemblies of mechanical oscillators. Here we report a novel and versatile technique for fabricating two-dimensional light-guiding arrays of mechanically compliant glass nanospikes with lengths up to several hundred μm. The procedure starts with a multicore fiber made by stacking and drawing capillaries and rods of two different germanate glasses with markedly different acid etching rates. After a suitable etching step, a free-standing nanospike array is created at the fiber end-face. The parameters are chosen so that there is evanescent coupling between adjacent nanospikes, which gives rise to strong optomechanical forces that can be exploited to drive and control the mechanical motion of the nanospikes and thus the optical properties.
CRIS-Team Scopus Importer:2019-10-18
Keywords: Multicore fiber; Nanospike array; Optical forces; Optomechanics; Soft-glass fiber

Optically Monitored Catalytic Photonic Crystal Fibre Microreactor - Cubillas, Ana Maria; Schmidt, Matthias; Euser, Tijmen G.; Etzold, Bastian; Taccardi, Nicola; Unterkofler, Sarah; Wasserscheid, Peter; Russell, Philip St. John (European Conference on Lasers and Electro-Optics, 2013)
Here we show that by depositing metallic catalyst nanoparticles in the core of the fibre, we can turn the HC-PCF into a catalytically active microreactor. As a proof-of-principle experiment, we investigated the well-known catalytic hydrogenation of azobenzene in a kagomé HC-PCF, whose core wall has been decorated with rhodium (Rh) catalyst nanoparticles. The reaction was monitored online by in-fibre absorption spectroscopy.

Optical measurement methods for refractive microlenses and microlens arrays - Lindlein, Norbert; et al. (Proceedings of SPIE, 2001)
UnivIS-Import:2015-03-09:Pub.2001.nat.dphy.optik.1optik.optica

Optical Memory Based on Conterpropagating Light in Microresonators - Bino, Leonardo Del; Moroney, Niall; Del'Haye, Pascal (2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021, 2021)
A consequence of the Kerr effect in ring microresonators is that light can not always circulate simultaneously in both directions. Instead, under the appropriate conditions of input power and detuning, light can couple into the resonator only in one direction while the other continues on the coupling waveguide [1] - [3]. The two resulting light states, clockwise (CW) and counterclockwise (CCW), can be interpreted as the digital states 1 and 0 as shown in Fig. 1 (c). Microresonators have been theorized to be a suitable solution for on-chip logical processing and switching [4]. Here we present an all-optical bistable device based on the difference of the Kerr effect for co-propagating and counterpropagating light. The device does not require any electrical power, and relies only on a single laser input for its operation. The optical state is set by the dominant input power direction. The system exhibits hysteresis ( Fig. 1 (d) ) hence the optical state is maintained until an significant input in the opposite direction is received. The hysteresis provides resilience to fluctuations in the inputs up to half of the total input power.
CRIS-Team Scopus Importer:2021-10-29

Optical properties of a tilted polarizer and geometric spin hall effect of light - Korger, Jan; Aiello, Andrea; Gabriel, Christian; Banzer, Peter; Kolb, Tobias; Marquardt, Christoph; Leuchs, Gerd (Optics InfoBase Conference Papers, 2011)
CRIS-Team Scopus Importer:2022-06-05

Optical Range Sensing with spatially modulated Coherence - Häusler, Gerd; et al. (Proc. of the Int. Symp. on Laser Applications in Precision Measurements, 1996)
UnivIS-Import:2015-04-16:Pub.1996.nat.dphy.optik.1optik.optica

Optical signal Regeneration at Different Modulation Formats - Schmauß, Bernhard; Striegler, Arne; Meißner, Markus (Proceedings of SPIE, 2004)
Optical transmission systems made impressive progress in the field of system capacity, reach and flexibility. Beside all improvements achieved so far, signal distortion on the one hand side and noise accumulation on the other hand side are the limitations of optical transmission systems. In terms of signal distortion besides advanced link design strategies optical regenerators are of high interest for signal conditioning along a fiber link. Furthermore the upcoming techniques of advanced modulation formats build a basis for further improvement of transmission quality that ends up with even higher reach, higher robustness against transmission impairments, lower signal to noise requirements etc. In this talk the current status of research in the field of optical signal regenerators suitable for signal regeneration for different modulation formats will be reviewed and presented, where we restrict our analysis to 2R regenerators. The focus will be put on regenerators taking advantage of non linear optical effects in order to improve signal quality. The main challenge is the treatment of phase modulated signals within regenerators. Especially the differential phase shift keying (DPSK) modulation format or the duobinary modulation format are attractive candidates for such kind of regenerators for further improvement of DPSK based transmission systems. The paper will go through several regenerative concepts like non linear optical loop mirror (NOLM) based and cross phase modulation based regenerators in order to figure out their potential for advanced modulation format based systems.
UnivIS-Import:2015-03-09:Pub.2004.nat.dphy.optik.1optik.optica
Keywords: Modulation Format; Optical Transmission; Regeneration

Optical signatures of the coupled spin-mechanics of a levitated magnetic microparticle - Wachter, Vanessa; Bittencourt, Victor A. S. V.; Xie, Shangran; Sharma, Sanchar; Joly, Nicolas; Russell, Philip St. John; Marquardt, Florian; Viola Kusminskiy, Silvia (Journal of the Optical Society of America B-Optical Physics, 2021)
We propose a platform that combines the fields of cavity optomagnonics and levitated optomechanics to control and probe the coupled spin-mechanics of magnetic dielectric particles. We theoretically study the dynamics of a levitated Faraday-active dielectric microsphere serving as an optomagnonic cavity, placed in an external magnetic field and driven by an external laser. We find that the optically driven magnetization dynamics induces angular oscillations of the particle with low associated damping. Further, we show that the magnetization and angular motion dynamics can be probed via the power spectrum of the outgoing light. Namely, the characteristic frequencies attributed to the angular oscillations and the spin dynamics are imprinted in the light spectrum by two main resonance peaks. Additionally, we demonstrate that a ferromagnetic resonance setup with an oscillatory perpendicular magnetic field can enhance the resonance peak corresponding to the spin oscillations and induce fast rotations of the particle around its anisotropy axis. (C) 2021 Optical Society of America
Created from Fastlane, WoS look-up

Optical simulations of printed Polymer Optical Waveguides (POWs): search for their optical limitations caused by fabrication and application geometry - Backhaus, Carsten; Vögl, Christian; Zeitler, Jochen Tobias; Reitberger, Thomas; Lindlein, Norbert; Franke, Jörg (2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, 2019)
Keywords: Polymer waveguides; Polymethyl methacrylate; Refractive index; Roughness; Surfaces; Systems design

Optical Testing of Refractive Microlenses - Lindlein, Norbert; et al. (Technisches Messen, 2002)
Microlens testing requires in many cases the measurement of surface deviations and the measurement of the wave aberrations of the lens. The lens function is for the multitude of microlenses brought about through curved surfaces of dielectric substrates. Only GRIN lenses rely on the three-dimensional distribution of the refractive index. For the measurement of the surface deviations the Twyman-Green interferometer and for cylinder lenses the grazing incidence test using diffractive beam splitters are best suited. Wave aberrations should be measured in single pass geometry because of systematic errors in case of big aberrations due to double pass arrangements. Therefore, the Mach-Zehnder on the one hand and the shearing interferometer on the other can be recommended for microlens tests. At the time being also wave front sensor as the Shack-Hartmann test are becoming a suitable alternative to the shearing methods because of its simplicity and sufficient sensitivity. A special field is the test of whole lens arrays. This concerns the paraxial as well as the aberration data. Low aperture lens arrays might be illuminated with plane waves indicating the uniformity of the lens data if a whole field is evaluated simultaneously.
Keywords: Aberrations measurement; Diffractive beam splitters; Interferometry; Microlenses; Wave front sensors

Optical Tomography: 3D-Metrology in Scattering Media - Häusler, Gerd; et al. (3D-Image Analysis and Synthesis, 1996)
UnivIS-Import:2015-04-20:Pub.1996.nat.dphy.optik.1optik.optica_1

Optical Transient Suppression using Stimulated Raman Attenuation - Holtmannspötter, Michael; Stephan, C.; Onishchukov, Georgy; Leuchs, Gerd; Schmauß, Bernhard (ECOC, September, 2008)
Dynamic optical attenuation based on the Raman Effect is investigated experimentally. The suppression of optical power transients as they arise from dynamic processes of EDFAs is shown. © 2008 IEEE.
UnivIS-Import:2015-04-16:Pub.2008.tech.IE.LEH.optica_3

Optical trapping of nanoparticles by full solid-angle focusing - Salakhutdinov, Vsevolod; Sondermann, Markus; Carbone, Luigi; Giacobino, Elisabeth; Bramati, Alberto; Leuchs, Gerd (Optica, 2016)
Optical dipole traps are used for trapping and localizing particles in various scientific fields,including classical optics,quantum optics,and biophysics. Here,we propose and implement a dipole trap for nanoparticles that is based on focusing from the full solid angle with a deep parabolic mirror. The key aspect is the generation of a linear-dipole mode,which is predicted to provide a tight trapping potential. We demonstrate the trapping of rod-shaped nanoparticles and validate the trapping frequencies to be of the order of the expected ones. The described realization of an optical trap is applicable for various other kinds of solid-state targets. The obtained results demonstrate the feasibility of optical dipole traps that simultaneously provide high trap stiffness and allow for efficient interaction of light and matter in free space.
Keywords: (260.5430) Polarization; (270.0270) Quantum optics; (350.4855) Optical tweezers or optical manipulation

Optics in Curved Space - Schultheiß, Vincent; Batz, Sascha; Szameit, Alexander; Dreisow, Felix; Nolte, Stefan; Tuennermann, Andreas; Longhi, Stefano; Peschel, Ulf (Physical Review Letters, 2010)
We experimentally study the impact of intrinsic and extrinsic curvature of space on the evolution of light. We show that the topology of a surface matters for radii of curvature comparable with the wavelength, whereas for macroscopically curved surfaces only intrinsic curvature is relevant. On a surface with constant positive Gaussian curvature we observe periodic refocusing, self-imaging, and diffractionless propagation. In contrast, light spreads exponentially on surfaces with constant negative Gaussian curvature. For the first time we realized two beam interference in negatively curved space.
EAM Import::2019-03-08

Optikprüfung von refraktiven Mikrolinsen - Leuchs, Gerd; Lindlein, Norbert; et al. (Technisches Messen, 2002)
UnivIS-Import:2015-03-09:Pub.2002.nat.dphy.optik.1optik.optikp

Optimally cloned binary coherent states - Müller, Christian; Leuchs, Gerd; Marquardt, Christoph; Andersen, U. L. (Physical Review A, 2017)
Binary coherent state alphabets can be represented in a two-dimensional Hilbert space. We capitalize this formal connection between the otherwise distinct domains of qubits and continuous variable states to map binary phase-shift keyed coherent states onto the Bloch sphere and to derive their quantum-optimal clones. We analyze the Wigner function and the cumulants of the clones, and we conclude that optimal cloning of binary coherent states requires a nonlinearity above second order. We propose several practical and near-optimal cloning schemes and compare their cloning fidelity to the optimal cloner.
CRIS-Team Scopus Importer:2022-06-05

Optimal spatial mode distributions for the coupling of a single photon to an atomic dipole transition in free space - Lindlein, Norbert; et al. (CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009)

Optimal working points for continuous-variable quantum channels - Khan, Imran; Wittmann, Christoffer; Jain, Nitin; Killoran, Nathan; Luetkenhaus, Norbert; Marquardt, Christoph; Leuchs, Gerd (Physical Review A - Atomic, Molecular, and Optical Physics, 2013)
The most important ability of a quantum channel is to preserve the quantum properties of transmitted quantum states. We experimentally demonstrate a continuous-variable system for efficient benchmarking of quantum channels. We probe the tested quantum channels for a wide range of experimental parameters such as amplitude, phase noise, and channel lengths up to 40 km. The data is analyzed using the framework of effective entanglement. We subsequently are able to deduce an optimal point of operation for each quantum channel with respect to the rate of distributed entanglement. This procedure is a promising candidate for benchmarking quantum nodes and individual links in large quantum networks of different physical implementations. © 2013 American Physical Society.
CRIS-Team Scopus Importer:2022-06-05

Optimierte Segmentierung der Papille in HRT-Retinaaufnahmen - Arold, Oliver; Bock, Rüdiger; Meier, Jörg; Michelson, Georg; Hornegger, Joachim (Bildverarbeitung für die Medizin 2008 - Algorithmen, Systeme, Anwendungen, 2008)

Optimised exposure strategies for artifial waveplates - Harder, Irina; Lohse, Olga; Rothau, Sergej; Piaszenski, Guido (39th International Conference on Micro and Nano Engineering, 2013)

Optimization of a nonlinear amplifying loop mirror for amplitude regeneration in phase-shift-keyed transmission - Sponsel, Klaus; Cvecek, Kristian; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE Photonics Technology Letters, 2007)
We present the numerical optimization of the transmission characteristics of a nonlinear amplifying loop mirror for amplitude regeneration of phase-encoded optical transmission formats. Adjusting the splitting factor, the amplifier gain and the phase bias, minimal phase distortions can be achieved while strong amplitude fluctuations are regenerated. The limiting effects of noise from the built-in amplifier and of amplified Rayleigh backscattering are also discussed. © 2007 IEEE.
UnivIS-Import:2015-03-09:Pub.2007.nat.dphy.optik.1optik.optimi
Keywords: 2R-regeneration; All-optical regeneration; Differential phase-shift keying; Nonlinear amplifying loop mirror

Optimization of Dispersion-Imbalanced Loop Mirror for Phase-Preserving Amplitude Regeneration - Röthlingshöfer, Tobias; Sponsel, Klaus; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE/LEOS Winter Topicals Meeting Series, 2009)
The adaptation and optimization of a dispersionimbalance loop mirror for phase-preserving amplitude 2R regeneration is shown by numerical simulations. Its performance has been evaluated for DPSK transmission. A 4.8dB Q-factor improvement has been demonstrated.
UnivIS-Import:2017-12-18:Pub.2009.tech.IE.LEH.optimi

Optimization of titanium and titanium alloy surface properties by ultra-short laser processing for improved antibacterial characteristics - Aceti, D. M.; Daskalova, A.; Angelova, L.; Filipov, E.; Sotelo, Lamborghini; Andreeva, A.; Trifonov, A.; Buchvarov, I. (Journal of Physics: Conference Series, 2022)
The aim of the current study is to improve in a one step process the properties of Ti and Ti alloy surfaces by enhancing their bioactivity in order to provide better conditions for microbial rejection. We propose to alter the biomaterial characteristics by a method alternative to the chemical ones, namely, non-contact processing of the surface by ultra-short laser pulses. The laser-induced modification results in a surface with different topographic features and an increased presence of oxides. We performed hierarchical laser patterning of the surface inducing the formation of areas covered by nanostructures, or laser-induced periodic surface structures (LIPSS), alternating with areas covered by micropillars in their turn surmounted by LIPSS. The increased roughness achieved due to the presence of micropillars, together with a marked presence of oxides, has been proven by several studies to enhance the biocompatibility of the material by improving the surface wettability and, furthermore, promoting the cells adhesion and osseointegration, while reducing the adhesion of pathogens. The laser processed surface, consisting of a pattern of parallel lines, showed improved and anisotropic wettability. The water contact angle value decreased by â1/410° in a direction orthogonal to the lines of the pattern, and by â1/440° in a parallel direction.
CRIS-Team Scopus Importer:2022-05-20

Optimization of white light interferometry at rough surfaces by error analysis - Häusler, Gerd; et al. (Optik, 2004)
White light interferometry can be used to measure the shape of rough surfaces. At rough surfaces, the measuring uncertainty in principle cannot be better than the surface roughness, which is commonly in the range of 1 micron. Hence, the requirements for the hard- and software components of the instrument are not as high as for interferometry in the nanometer regime. An analysis of the dominant error sources allows the design of an "optimal" sensor with a measuring uncertainty as small as physically possible, with components as good as necessary and as simple as possible.
UnivIS-Import:2015-03-09:Pub.2004.nat.dphy.optik.1optik.optimi
Keywords: Measuring uncertainty; White light interferometry

Optimized analysis for sensitive detection and analysis of single proteins via interferometric scattering microscopy - Mirzaalian Dastjerdi, Houman; Dahmardeh, Mahyar; Gemeinhardt, Andre; Mahmoodabadi, Reza Gholami; Köstler, Harald; Sandoghdar, Vahid (Journal of Physics D: Applied Physics, 2022)
It has been shown that interferometric detection of Rayleigh scattering (iSCAT) can reach an exquisite sensitivity for label-free detection of nano-matter, down to single proteins. The sensitivity of iSCAT detection is intrinsically limited by shot noise, which can be indefinitely improved by employing higher illumination power or longer integration times. In practice, however, a large speckle-like background and technical issues in the experimental setup limit the attainable signal-to-noise ratio. Strategies and algorithms in data analysis are, thus, crucial for extracting quantitative results from weak signals, e.g. regarding the mass (size) of the detected nano-objects or their positions. In this article, we elaborate on some algorithms for processing iSCAT data and identify some key technical as well as conceptual issues that have to be considered when recording and interpreting the data. The discussed methods and analyses are made available in the extensive python-based platform, PiSCAT(6).
CRIS-Team WoS Importer:2021-11-12

Optimizing the generation of polarization squeezed light in nonlinear optical fibers driven by femtosecond pulses - Andrianov, A. V.; Kalinin, Nikolay; Sorokin, A. A.; Anashkina, E. A.; Sánchez-Soto, L. L.; Corney, J. F.; Leuchs, Gerd (Optics Express, 2023)
Bright squeezed light can be generated in optical fibers utilizing the Kerr effect for ultrashort laser pulses. However, pulse propagation in a fiber is subject to nonconservative effects that deteriorate the squeezing. Here, we analyze two-mode polarization squeezing, which is SU(2)-invariant, robust against technical perturbations, and can be generated in a polarization-maintaining fiber. We perform a rigorous numerical optimization of the process and the pulse parameters using our advanced model of quantum pulse evolution in the fiber that includes various nonconservative effects and real fiber data. Numerical results are consistent with experimental results.
CRIS-Team Scopus Importer:2023-01-06

Optimum splitting ratio for amplifier noise reduction by an asymmetric nonlinear optical loop mirror - Meißner, Markus; Rösch, Matthias; Korolkova, Natalia; Sizmann, Andreas; Schmauß, Bernhard; Leuchs, Gerd (Optical Communication, 2002)
UnivIS-Import:2015-04-16:Pub.2002.nat.dphy.optik.1optik.optimu

Optimum splitting ratio for amplifier noise reduction by an asymmetric nonlinear optical loop mirror - Meißner, Markus; Rösch, Matthias; Schmauß, Bernhard; Leuchs, Gerd (Applied Physics B-Lasers and Optics, 2005)
We theoretically and experimentally analyze the influence of the splitting ratio and the input power on the noise reduction capability of an asymmetric nonlinear optical loop mirror (NOLM) for different input noise levels. An easy method to calculate the optimum parameters for noise reduction is also presented. The best noise reduction is found at NOLM input powers at which the nonlinear transfer function has a slope close to zero. Additionally, the splitting ratio of the NOLM has to be adapted to its input noise level to suppress amplitude fluctuations effectively. Since the noise reduction by the NOLM is due to the Kerr nonlinearity, which has a timescale below a few femtoseconds, the noise reduction is applicable to short pulses in the picosecond and femtosecond range. This makes the NOLM applicable as an optical regenerator in an optical data transmission system at high bit rates, such as 160 GBit/s. © Springer-Verlag 2005.
UnivIS-Import:2015-03-09:Pub.2005.nat.dphy.optik.1optik.optimu

Optimum splitting ratio for amplifier noise reduction vy an asymmetric nonlinear optical loop mirror - Schmauß, Bernhard; Meißner, Markus; Rösch, Matthias; Leuchs, Gerd (Applied Physics B, Febr., 2005)
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.optimu

Optische 3D-Messtechnik in der Mund-, Kiefer-, Gesichtschirurgie - Häusler, Gerd; Nkenke, Emeka; et al. (Informatik 2005 - Informatik live! (35. Jahrestagung der Ges. für Informatik e.V.), 2005)
UnivIS-Import:2015-04-20:Pub.2005.nat.dphy.optik.1optik.optisc

Optische 3D-Sensoren helfen dem Restaurator - Häusler, Gerd; et al. (Das moderne Museum - Die Vorträge der MUTEC 99, 2001)
UnivIS-Import:2015-04-16:Pub.2001.nat.dphy.optik.1optik.optisc

Optische 3D-Sensoren mit großem Meßbereich und hoher Genauigkeit - Häusler, Gerd; et al. (Info Phys Tech, 1995)
UnivIS-Import:2015-03-05:Pub.1995.nat.dphy.optik.1optik.optisc_7

Optische 3D-Sensoren und deren industrielle Anwendung - Häusler, Gerd; et al. (Technisches Messen, 1996)
UnivIS-Import:2015-03-05:Pub.1996.nat.dphy.optik.1optik.ptisch

Optische Messtechnik an diffus reflektierenden Medien - Häusler, Gerd; et al. (Expert-Verlag, 1997)
UnivIS-Import:2015-05-08:Pub.1997.nat.dphy.optik.1optik.mglich

Optischer Sensor wacht über Lasermaterialbearbeitung - Häusler, Gerd; et al. (F and M; Feinwerktechnik, Mikrotechnik, Messtechnik, 1995)
UnivIS-Import:2015-03-05:Pub.1995.nat.dphy.optik.1optik.optisc

Optoelectronic interconnects with holographic optical elements - Lindlein, Norbert; et al. (3rd International Conference on Holographic Systems, Components and Applications, 1991)
Highly efficient holographic optical elements (HOEs) in dichromated gelatin (DGG) have been demonstrated. Several systems and components will be presented: (1) interconnections based on a light guiding glass plate with holographic coupling elements, (2) permutation elements for optoelectronic switching systems, (3) holographic beamsplitters and (4) holographic microlens arrays.

Optofluidic immobility of particles trapped in liquid-filled hollow-core photonic crystal fiber - Garbos, M. K.; Euser, T. G.; Russell, Philip St. John (Optics Express, 2011)
We study the conditions under which a particle, laser-guided in a vertically-oriented hollow-core photonic crystal fiber filled with liquid, can be kept stationary against a microfluidic counter-flow. An immobility parameter—the fluid flow rate required to immobilize a particle against the radiation force produced by unit guided optical power—is introduced to quantify the conditions under which this occurs, including radiation, viscous and gravity forces. Measurements show that this parameter depends strongly on the ratio of particle radius a to core radius R, peaking at an intermediate value of a/R. The results follow fairly well the theoretical estimates of the optical (calculated approximately using a ray optics approach) and numerically simulated drag forces. We suggest that the system has potential applications in, e.g., measurement of the diameter, refractive index and density of particles, synthesis and biomedical research.
EAM Import::2019-03-08

Optofluidic rotation of living cells for single-cell tomography - Kolb, Thorsten; Albert, Sahradha; Haug, Michael; Whyte, Graeme (Journal of Biophotonics, 2014)
Flow cytometry provides a high throughput, multi-dimensional analysis of cells flowing in suspension. In order to combine this feature with the ability to resolve detailed structures in 3D, we developed an optofluidic device that combines a microfluidic system with a dual beam trap. This allows for the rotation of single cells in a continuous flow, around an axis perpendicular to the imaging plane. The combination of both techniques enables the tomographic reconstruction of the 3D structure of the cell. In addition this method is capable to provide detailed 3D structural data for flow cytometry, as it improves the reconstructed z-resolution of a standard microscopy system to produce images with isotropic resolution in all three axes.
EAM Import::2019-03-08

Optomechanical cooling and self-stabilization of a waveguide coupled to a whispering-gallery-mode resonator - Pennetta, Riccardo; Xie, Shangran; Zeltner, Richard; Hammer, Jonas; Russell, Philip St. John (Photonics Research, 2020)
Laser cooling of mechanical degrees of freedom is one of the most significant achievements in the field of optomechanics. Here, we report, for the first time to the best of our knowledge, efficient passive optomechanical cooling of the motion of a freestanding waveguide coupled to a whispering-gallery-mode (WGM) resonator. The waveguide is an 8 mm long glass-fiber nanospike, which has a fundamental flexural resonance at Ω/2Π = 2.5 kHz and a Q-factor of 1.2 × 105. Upon launching ∼250 μW laser power at an optical frequency close to the WGM resonant frequency, we observed cooling of the nanospike resonance from room temperature down to 1.8 K. Simultaneous cooling of the first higher-order mechanical mode is also observed. The strong suppression of the overall Brownian motion of the nanospike, observed as an 11.6 dB reduction in its mean square displacement, indicates strong optomechanical stabilization of linear coupling between the nanospike and the cavity mode. The cooling is caused predominantly by a combination of photothermal effects and optical forces between nanospike and WGM resonator. The results are of direct relevance in the many applications of WGM resonators, including atom physics, optomechanics, and sensing.
CRIS-Team Scopus Importer:2020-06-16

Orbital angular momentum modes of high-gain parametric down-conversion - Beltran, Lina; Frascella, Gaetano; Perez, Angela M.; Fickler, Robert; Sharapova, Polina R.; Manceau, Mathieu; Tikhonova, Olga V.; Boyd, Robert W.; Leuchs, Gerd; Chekhova, Maria V. (Journal of Optics, 2017)
Light beams with orbital angular momentum (OAM) are convenient carriers of quantum information. They can also be used for imparting rotational motion to particles and providing high resolution in imaging. Due to the conservation of OAM in parametric down-conversion (PDC), signal and idler photons generated at low gain have perfectly anti-correlated OAM values. It is interesting to study the OAM properties of high-gain PDC, where the same OAM modes can be populated with large, but correlated, numbers of photons. Here we investigate the OAM spectrum of high-gain PDC and show that the OAM mode content can be controlled by varying the pump power and the configuration of the source. In our experiment, we use a source consisting of two nonlinear crystals separated by an air gap. We discuss the OAM properties of PDC radiation emitted by this source and suggest possible modifications.
CRIS-Team Scopus Importer:2023-03-27
Keywords: bright squeezed vacuum; coherent modes; orbital angular momentum; parametric down-conversion; Schmidt modes

Orbital-to-spin angular momentum conversion employing local helicity - Nechayev, Sergey; Eismann, Jörg; Leuchs, Gerd; Banzer, Peter (Physical Review B, 2019)
Spin-orbit interactions in optics traditionally describe an influence of the polarization degree of freedom of light on its spatial properties. The most prominent example is the generation of a spin-dependent optical vortex upon focusing or scattering of a circularly polarized plane wave by a nanoparticle, converting spin to orbital angular momentum of light. Here we present a mechanism of conversion of orbital-to-spin angular momentum of light upon scattering of a linearly polarized vortex beam by a spherical silicon nanoparticle. We show that focused linearly polarized Laguerre-Gaussian beams of first order (l = +1) exhibit an -dependent spatial distribution of helicity density in the focal volume. By using a dipolar scatterer the helicity density can be manipulated locally, while influencing globally the spin and orbital angular momentum of the beam. Specifically, the scattered light can be purely circularly polarized with the handedness depending on the orbital angular momentum of the incident beam. We corroborate our findings with theoretical calculations and an experimental demonstration. Our work sheds light on the global and local properties of helicity conservation laws in electromagnetism.
CRIS-Team WoS Importer:2019-03-15

Organic Molecules as Origin of Visible-Range Single Photon Emission from Hexagonal Boron Nitride and Mica - Neumann, Michael; Wei, Xu; Morales-Inostroza, Luis; Song, Seunghyun; Lee, Sung Gyu; Watanabe, Kenji; Taniguchi, Takashi; Götzinger, Stephan; Lee, Young Hee (ACS nano, 2023)
The discovery of room-temperature single-photon emitters (SPEs) hosted by two-dimensional hexagonal boron nitride (2D hBN) has sparked intense research interest. Although emitters in the vicinity of 2 eV have been studied extensively, their microscopic identity has remained elusive. The discussion of this class of SPEs has centered on point defects in the hBN crystal lattice, but none of the candidate defect structures have been able to capture the great heterogeneity in emitter properties that is observed experimentally. Employing a widely used sample preparation protocol but disentangling several confounding factors, we demonstrate conclusively that heterogeneous single-photon emission at ∼2 eV associated with hBN originates from organic molecules, presumably aromatic fluorophores. The appearance of those SPEs depends critically on the presence of organic processing residues during sample preparation, and emitters formed during heat treatment are not located within the hBN crystal as previously thought, but at the hBN/substrate interface. We further demonstrate that the same class of SPEs can be observed in a different 2D insulator, fluorophlogopite mica.
CRIS-Team Scopus Importer:2023-07-07
Keywords: fluorophlogopite mica; hexagonal boron nitride; organic processing residue; polycyclic aromatic hydrocarbons; single photon emission

Overcoming detection loss and noise in squeezing-based optical sensing - Frascella, Gaetano; Agne, Sascha; Khalili, Farid Ya.; Chekhova, Maria (npj Quantum Information, 2021)
Among the known resources of quantum metrology, one of the most practical and efficient is squeezing. Squeezed states of atoms and light improve the sensing of the phase, magnetic field, polarization, mechanical displacement. They promise to considerably increase signal-to-noise ratio in imaging and spectroscopy, and are already used in real-life gravitational-wave detectors. But despite being more robust than other states, they are still very fragile, which narrows the scope of their application. In particular, squeezed states are useless in measurements where the detection is inefficient or the noise is high. Here, we experimentally demonstrate a remedy against loss and noise: strong noiseless amplification before detection. This way, we achieve loss-tolerant operation of an interferometer fed with squeezed and coherent light. With only 50% detection efficiency and with noise exceeding the level of squeezed light more than 50 times, we overcome the shot-noise limit by 6 dB. Sub-shot-noise phase sensitivity survives up to 87% loss. Application of this technique to other types of optical sensing and imaging promises a full use of quantum resources in these fields.
CRIS-Team WoS Importer:2021-05-21

Overcoming detection losses in a supersensitive interferometer with coherent and squeezed vacuum inputs - Frascella, Gaetano; Agne, Sascha; Khalili, Farid Ya; Chekhova, Maria (Optics InfoBase Conference Papers, 2020)
We report phase sensitivity overcoming the shot-noise limit by 3 dB for a squeezing-assisted interferometer with 50% detection losses. The performance is tolerant to losses up to 87% because of an optical parametric amplifier at the output.
CRIS-Team Scopus Importer:2020-11-13

Overcoming inefficient detection in sub-shot-noise absorption measurement and imaging - Knyazev, Eugene; Khalili, Farid Ya; Chekhova, Maria (Optics Express, 2019)
Photon-number squeezing and correlations enable measurement of absorption with an accuracy exceeding that of the shot-noise limit. However, sub-shot noise imaging and sensing based on these methods require high detection efficiency, which can he a serious obstacle it measurements are carried out in "difficult" spectral ranges. We show that this problem can he overcome through the phase-sensitive amplification before detection. Here we propose an experimental scheme of sub-shot-noise imaging with tolerance to detection losses. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
CRIS-Team WoS Importer:2019-03-29

Overcoming vacuum noise: The unforeseen benefits of quantum heterodyne detection - Müller, C. R.; Peuntinger, C.; Dirmeier, T.; Khan, I.; Vogl, U.; Marquardt, Christoph; Leuchs, Gerd; Sánchez-Soto, L. L.; Teo, Y. S.; Hradil, Z.; Rehácek, J. (Optics InfoBase Conference Papers, 2016)
Homodyne tomography and heterodyne detection are principal measurement schemes in continuous-variable quantum information and provide different accuracies in determining the quantum state of a system. The former allows for a tomographic reconstruction of the Wigner function of the state, whereas the latter directly samples its Husimi Q-function. We experimentally demonstrate that contrary to a common belief, heterodyne detection outperforms homodyne tomography for almost all Gaussian states.
CRIS-Team Scopus Importer:2022-06-05

Painting by numbers: Nanoparticle-based colorants in the post-empirical age - Klupp Taylor, Robin; Seifrt, Frantiek; Zhuromskyy, Oleksandr; Peschel, Ulf; Leugering, Günter; Peukert, Wolfgang (Advanced Materials, 2011)
The visual appearance of the artificial world is largely governed by films or composites containing particles with at least one dimension smaller than a micron. Over the past century and a half, the optical properties of such materials have been scrutinized and a broad range of colorant products, based mostly on empirical microstructural improvements, developed. With the advent of advanced synthetic approaches capable of tailoring particle shape, size and composition on the nanoscale, the question of what is the optimum particle for a certain optical property can no longer be answered solely by experimentation. Instead, new and improved computational approaches are required to invert the structure-function relationship. This progress report reviews the development in our understanding of this relationship and indicates recent examples of how theoretical design is taking an ever increasingly important role in the search for enhanced or multifunctional colorants. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Keywords: colloids; core/shell nanoparticles; designed nanostructures; functional coatings; structure-property relationships

Parallel optoelectronic interconnections with high packing density through a light-guiding plate using grating couplers and field lenses - Lindlein, Norbert; et al. (Optics Communications, 1993)
Optoelectronic interconnections between boards at 1-100 cm distances are proposed, which are based on a typically some 5- 10 mm thick light-guiding plate for confinement and transport of the optical signals with low loss, on the order of 0.1 dB/cm. The plate is equipped with grating couplers fabricated as volume phase holograms in dichromated gelatin with insertion loss as low as 0.5 dB/coupler. The apertures of the optoelectronic transmitters are imaged onto the apertures of the receivers by aspheric field lenses or mirrors mounted on the plate. Such optical systems render packing densities as high as 1000 channel/cm possible that are required for the application of densely packed integrated arrays of semiconductor lasers and detectors. Grating dispersion, axial astigmatism, geometrical distortion and coma are eliminated in the proposed optical setup. Results from ray tracing and an experiment are presented. © 1993.

Parallel two-step phase-shifting point-diffraction interferometry for microscopy based on a pair of cube beamsplitters - Peng, Gao; Yao, Baoli; Min, Junwei; Harder, Irina; Nercissian, Vanusch; Mantel, Klaus; Guo, Rongli; Zheng, Juanjuan; Ye, Tong (Optics Express, 2011)

Parity Measurement in Action: Detecting Errors in the Surface Code and Heralding itinerant Cat States using Superconducting Circuits - Eichler, Christopher (MPI for the Science of Light:, 2020)
Parity Measurements in Action: Detecting Errors in the Surface Code and Heralding Itinerant Cat States using Superconducting Circuits. Parity measurements distinguish between quantum states with an even and an odd number of excitations without revealing any additional information about the state. Nondestructive parity detection allows one to project onto highly entangled states and therefore plays a central role in quantum error correction. In my talk, I discuss two complementary implementations of parity detection both realized in superconducting circuits. First, we measure the parity of the photon number of propagating radiation fields and thereby herald itinerant Schrödinger cat states [1]. Second, we perform ancilla-based parity detection in multi-qubit systems to implement the smallest viable instance of the surface code capable of detecting any single error [2]. Both experiments crucially rely on recent progress in performing high-fidelity, fast, and qubit-selective readout [3], and highlight the great potential of superconducting circuits for quantum information science. [1] J. - C. Besse, S. Gasparinetti, M. C. Collodo, T. Walter, A. Remm, J. Krause, C. Eichler, and A. Wallraff, arXiv:1912.09896 (2019); J. - C. Besse, S. Gasparinetti, M. C. Collodo, T. Walter, P. Kurpiers, M. Pechal, C. Eichler, and A. Wallraff, Phys. Rev. X 8, 021003 (2018) [2] C. Kraglund Andersen, A. Remm, S. Lazar, S. Krinner, N. Lacroix, G. J. Norris, M. Gabureac, C. Eichler, and A. Wallraff, arXiv:1912.09410 (2019); C. Kraglund Andersen*, A. Remm*, S. Lazar, S. Krinner, J. Heinsoo, J-C. Besse, M. Gabureac, A. Wallraff, and C. Eichler, NPJ Quantum Information 5, 69 (2019) [3] J. Heinsoo, C. Kraglund Andersen, A. Remm, S. Krinner, T. Walter, Y. Salathe, S. Gasparinetti, J-C. Besse, A. Potocnik, A. Wallraff, and C. Eichler, Phys. Rev. Applied 10, 034040 (2018); T. Walter, P. Kurpiers, S. Gasparinetti, P. Magnard, A. Potoćnik, Y. Salathe, M. Pechal, M. Mondal, M. Oppliger, C. Eichler, and A. Wallraff, Phys. Rev. Applied 7, 054020 (2017)
Keywords: wwwqudev

Parity Measurements in Action: Detecting Errors in the Surface Code and Heralding itinerant Cat States using Superconducting Circuits - Eichler, Christopher (MPI for Quantum Optics (MPQ), 2020)
Parity Measurements in Action: Detecting Errors in the Surface Code and Heralding Itinerant Cat States using Superconducting Circuits. Parity measurements distinguish between quantum states with an even and an odd number of excitations without revealing any additional information about the state. Nondestructive parity detection allows one to project onto highly entangled states and therefore plays a central role in quantum error correction. In my talk, I discuss two complementary implementations of parity detection both realized in superconducting circuits. First, we measure the parity of the photon number of propagating radiation fields and thereby herald itinerant Schrödinger cat states [1]. Second, we perform ancilla-based parity detection in multi-qubit systems to implement the smallest viable instance of the surface code capable of detecting any single error [2]. Both experiments crucially rely on recent progress in performing high-fidelity, fast, and qubit-selective readout [3], and highlight the great potential of superconducting circuits for quantum information science. [1] J. - C. Besse, S. Gasparinetti, M. C. Collodo, T. Walter, A. Remm, J. Krause, C. Eichler, and A. Wallraff, arXiv:1912.09896 (2019); J. - C. Besse, S. Gasparinetti, M. C. Collodo, T. Walter, P. Kurpiers, M. Pechal, C. Eichler, and A. Wallraff, Phys. Rev. X 8, 021003 (2018) [2] C. Kraglund Andersen, A. Remm, S. Lazar, S. Krinner, N. Lacroix, G. J. Norris, M. Gabureac, C. Eichler, and A. Wallraff, arXiv:1912.09410 (2019); C. Kraglund Andersen*, A. Remm*, S. Lazar, S. Krinner, J. Heinsoo, J-C. Besse, M. Gabureac, A. Wallraff, and C. Eichler, NPJ Quantum Information 5, 69 (2019) [3] J. Heinsoo, C. Kraglund Andersen, A. Remm, S. Krinner, T. Walter, Y. Salathe, S. Gasparinetti, J-C. Besse, A. Potocnik, A. Wallraff, and C. Eichler, Phys. Rev. Applied 10, 034040 (2018); T. Walter, P. Kurpiers, S. Gasparinetti, P. Magnard, A. Potoćnik, Y. Salathe, M. Pechal, M. Mondal, M. Oppliger, C. Eichler, and A. Wallraff, Phys. Rev. Applied 7, 054020 (2017)
Keywords: wwwqudev

Parity-time synthetic photonic lattices - Regensburger, Alois; Bersch, Christoph; Miri, Mohammad-Ali; Onishchukov, Georgy; Christodoulides, Demetrios N.; Peschel, Ulf (Nature, 2012)
The development of new artificial structures and materials is today one of the major research challenges in optics. In most studies so far, the design of such structures has been based on the judicious manipulation of their refractive index properties. Recently, the prospect of simultaneously using gain and loss was suggested as a new way of achieving optical behaviour that is at present unattainable with standard arrangements. What facilitated these quests is the recently developed notion of `parity–time symmetry' in optical systems, which allows a controlled interplay between gain and loss. Here we report the experimental observation of light transport in large-scale temporal lattices that are parity–time symmetric. In addition, we demonstrate that periodic structures respecting this symmetry can act as unidirectional invisible media when operated near their exceptional points. Our experimental results represent a step in the application of concepts from parity–time symmetry to a new generation of multifunctional optical devices and networks.
EAM Import::2019-03-08

Parsing polarization squeezing into Fock layers - Müller, Christian; Madsen, Lars S.; Klimov, Andrei B.; Sanchez-Soto, Luis L.; Leuchs, Gerd; Marquardt, Christoph; Andersen, Ulrik L. (Physical Review A, 2016)
We investigate polarization squeezing in squeezed coherent states with varying coherent amplitudes. In contrast to the traditional characterization based on the full Stokes parameters, we experimentally determine the Stokes vector of each excitation subspace separately. Only for states with a fixed photon number do the methods coincide; when the photon number is indefinite, we parse the state in Fock layers, finding that substantially higher squeezing can be observed in some of the single layers. By capitalizing on the properties of the Husimi Q function, we map this notion onto the Poincaré space, providing a full account of the measured squeezing.
CRIS-Team Scopus Importer:2022-06-05

Partial Cloaking of a Gold Particle by a Single Molecule - Zirkelbach, Johannes; Gmeiner, Benjamin; Renger, Jan; Tuerschmann, Pierre; Utikal, Tobias; Götzinger, Stephan; Sandoghdar, Vahid (Physical Review Letters, 2020)
Extinction of light by material particles stems from losses incurred by absorption or scattering. The extinction cross section is usually treated as an additive quantity, leading to the exponential laws that govern the macroscopic attenuation of light. In this Letter, we demonstrate that the extinction cross section of a large gold nanoparticle can be substantially reduced-i.e., the particle becomes more transparent-if a single molecule is placed in its near field. This partial cloaking effect results from a coherent plasmonic interaction between the molecule and the nanoparticle, whereby each of them acts as a nanoantenna to modify the radiative properties of the other.
CRIS-Team WoS Importer:2020-09-18

Perfect excitation of a matter qubit by a single photon in free space - Leuchs, Gerd; et al. (EPL - Europhysics Letters, 2009)
We propose a scheme for perfect excitation of a single two-level atom by a single photon in free space. The photon state has to match the time reversed photon state originating from spontaneous decay of a two-level system. Here, we discuss its experimental preparation. The state is characterized by a particular asymmetric exponentially shaped temporal profile. Any deviations from this ideal state limit the maximum absorption. Although perfect excitation requires an infinite amount of time, we demonstrate that there is a class of initial one-photon quantum states which can achieve almost perfect absorption even for a finite interaction time. Our results pave the way for realizing perfect coupling between flying and stationary qubits in free space thus opening a possibility for building scalable quantum networks. © EPLA, 2009.
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.optik.1optik.perfec

Perfect imaging of hypersurfaces via transformation optics - Mantel, Klaus; Peschel, Ulf; Bachstein, Dustin (Optics Letters, 2011)

Perfect Imaging of Planes and Surfaces via Transformation Optics - Bachstein, Dustin; Mantel, Klaus; Peschel, Ulf (Proc. 5th EOS Topical Meeting on Advanced Imaging Techniques, ISBN 978-3-00-030503-0, 2010)

Performance analysis of simultaneous multilevel amplitude and phase regeneration - Röthlingshöfer, Tobias; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (39th European Conference and Exhibition on Optical Communication (ECOC), 2013)
A star-8QAM regeneration was investigated in numerical simulations for two schemes: a combined NALM with a PSA in the loop and a cascade of PSA and NALM. Significant improvements in error vector magnitude and bit error rate are achieved for both schemes in a transmission system limited by amplified spontaneous emission and nonlinear phase noise.
lhft_intern.bib::Roethlingshoefer2013a

Perturbation theory of nearly spherical dielectric optical resonators - Gohsrich, Julius; Shah, Tirth; Aiello, Andrea (Physical Review A, 2021)
Dielectric spheres of various sizes may sustain electromagnetic whispering-gallery modes resonating at optical frequencies with very narrow linewidths. Arbitrary small deviations from the spherical shape typically shift and broaden such resonances. Our goal is to determine these shifted and broadened resonances. A boundary-condition perturbation theory for the acoustic vibrations of nearly circular membranes was developed by Rayleigh more than a century ago. We extend this theory to describe the electromagnetic excitations of nearly spherical dielectric cavities. This approach permits us to avoid dealing with decaying quasinormal modes. We explicitly find the frequencies and the linewidths of the optical resonances for arbitrarily deformed nearly spherical dielectric cavities, as power series expansions by a small parameter, up to and including second-order terms. We thoroughly discuss the physical conditions for the applicability of perturbation theory.
CRIS-Team WoS Importer:2021-09-03

Phase and polarization measurement of a spatially varying linear polarization distribution - Rothau, Sergej; Nercissian, Vanusch; Berger, Andreas; Harder, Irina; Mantel, Klaus Peter; Lindlein, Norbert (7th International Workshop on Advanced Optical Imaging and Metrology, Fringe 2013, 2013)
The first measurements show very good results and are consistent with the theory. The next step is the study of measurement results made with further combinations of φi and ωi and the investigation of their robustness against stochastic errors or the influence of elliptical polarization. © Springer-Verlag Berlin Heidelberg 2014.

Phase-locking an interferometer with single-photon detections - Hacker, Bastian; Günthner, Kevin; Rößler, Conrad; Marquardt, Christoph (New Journal of Physics, 2023)
We report on a novel phase-locking technique for fiber-based Mach-Zehnder interferometers based on discrete single-photon detections, and demonstrate this in a setup. Our interferometer decodes relative-phase-encoded optical pulse pairs for quantum key distribution applications and requires no locking laser in addition to the weak received signal. Our new simple locking scheme is shown to produce an Ornstein-Uhlenbeck dynamic and achieve optimal phase noise for a given count rate. In case of wavelength drifts that arise during the reception of Doppler-shifted satellite signals, the arm-length difference gets continuously readjusted to keep the interferometer phase stable.
CRIS-Team Scopus Importer:2023-12-01
Keywords: feedback; interferometry; Mach-Zehnder; phase-locking; quantum communication; quantum key distribution; single-photon detection

Phase-locking of multiple acoustic resonances by intense optomechanical interactions in a soliton fiber laser - Yeh, Dung Han; He, Wenbin; Pang, Meng; Jiang, Xin; Russell, Philip St. John (Optics InfoBase Conference Papers, 2020)
In a soliton fiber laser incorporating three different PCF sections and optomechanically mode-locked at around 1.94 GHz, the three acoustic core resonances are strongly driven, coupled and phase-locked by the sequence of laser pulses.
CRIS-Team Scopus Importer:2020-11-13

Phase measurement of a spatially varying polarization distribution - Nercissian, Vanusch; Geier, Florian; Berger, Andreas; Rothau, Sergej; Ghadyani, Zahra; Harder, Irina; Mantel, Klaus Peter; Lindlein, Norbert (DGaO Proceedings, 2012)

Phase Measuring Deflectometry: a new approuch to measure specular free-form surfaces - Häusler, Gerd; et al. (Proceedings of SPIE, 2004)
UnivIS-Import:2015-03-09:Pub.2004.nat.dphy.optik.1optik.phasem

Phase noise suppression in Microstructured Fibers - Korn, Alexander; Glöckl, Oliver; Lorenz, Stefan; Marquardt, Christoph; Andersen, Ulrik Lund; Leuchs, Gerd (International Quantum Electronics Conference 2004, 2004)
We investigated thermal phase-noise in a microstructured fiber. We demonstrate that the microstructure of the fiber establishes a low order acoustic resonator thus suppressing all guided acoustic wave Brillouin scattering modes up to 300 MHz.<br

Phase-Preserving 2R-Regeneration of an 80-Gb/s RZ-DQPSK, Signal by Using a Nonlinear Amplifying Loop Mirror - Cvecek, Kristian; Sponsel, Klaus; Stephan, Christian; Ludwig, R.; Schubert, Christina; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (ECOC September, 2007)
The performance of a nonlinear amplifying loop mirror as a 2R regenerator for an 80-Gb/s RZ-DQPSK has been investigated. A significant eye-opening improvement and a negative power penalty of 2.6 dB have been obtained.
UnivIS-Import:2017-12-18:Pub.2007.tech.IE.LEH.phasep

Phase-Preserving 2R-Regeneration of a WDM RZ-DPSK Signal Using a Nonlinear Amplifying Loop Mirror - Cvecek, Kristian; Sponsel, Klaus; Stephan, C.; Onishchukov, Georgy; Ludwig, R.; Schubert, C.; Schmauß, Bernhard; Leuchs, Gerd (Optical Communication / National Fiber Optic Engineers Conference OFC/NFOEC 24.-28.02., 2008)
A modified NALM setup for phase-preserving amplitude regeneration of WDM-DPSK signals is proposed. Demultiplexing-multiplexing within the NALM fiber loop is used to avoid WDM channel crosstalk, A negative power penalty of 1.2 dB was obtained. © 2007 Optical Society of America.
UnivIS-Import:2017-11-07:Pub.2008.tech.IE.LEH.phasep

Phase preserving 2R-Regeneration using a nonlinear optical loop mirror - Cvecek, Kristian; Striegler, Arne; Meißner, Markus; Sponsel, Klaus; Schmauß, Bernhard; Leuchs, Gerd (Cleo/Europe EQEC Conference, Munich, Germany, June, 2005)
In our experiment a NOLM regenerator is adapted for reducing amplitude jitter of a DPSK signal without destroying the phase information.
UnivIS-Import:2015-04-16:Pub.2005.tech.IE.LEH.phasep

Phase-preserving amplitude noise suppression using an attenuation-imbalanced NOLM - Parsons, E.; Stephan, K.; Sponsel, K.; Roethlingshoefer, T; Kueppers, F.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (Proc. SPIE, 7621, 762109, Jan., 2010)
lhft_intern.bib::Parsons10

Phase-preserving amplitude regeneration for a WDM RZ-DPSK signal using a nonlinear amplifying loop mirror - Onishchukov, Georgy; Cvecek, Kristian; Sponsel, Klaus; Stephan, Christian; Ludwig, R.; Schubert, C.; Schmauß, Bernhard; Leuchs, Gerd (Optics Express, 2008)
We propose a modified nonlinear amplifying loop mirror (NALM) for phase-preserving 2R regeneration of wavelength division multiplexed (WDM) return-to-zero differential phase-shift-keyed signals. As proof of principle the regeneration capability of this NALM setup has been investigated experimentally for two 10 Gbit/s wavelength channels. A significant eye-opening improvement and a negative power penalty of 1.2 dB have been observed in both channels. © 2008 Optical Society of America.
UnivIS-Import:2015-03-09:Pub.2008.nat.dphy.optik.1optik.phasep

Phase-Preserving Amplitude Regeneration in DPSK Transmission Systems Using a Nonlinear Amplifying Loop Mirror - Stephan, Christian; Sponsel, Klaus; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (IEEE Journal of Quantum Electronics, 2009)
A phase-preserving 2R regenerator based on a nonlinear amplifying loop mirror was implemented in a RZ-DPSK transmission system. Its performance has been investigated in numerical simulations and experimentally. The results show that amplitude regeneration using a NALM can efficiently prevent accumulation of nonlinear phase noise in a 10 Gb/s DPSK transmission system. In the experiments, significant improvements of eye opening and of BER as well as a 3 dB increase in fiber launch power have been demonstrated. Simulations at 10 Gb/s and 100 Gb/s indicated that the enhancement of the transmission quality is smaller at 100 Gb/s. The reason is that at 100 Gb/s nonlinear intra-channel effects rather than pure nonlinear phase noise are the main limiting factor and the NALM can only reduce the accumulation of amplitude noise in that case. © 2009 IEEE.
UnivIS-Import:2015-03-09:Pub.2009.nat.dphy.optik.1optik.phasep
Keywords: 2R regeneration; Differential phase-shift keying; Nonlinear amplifying loop mirror; Nonlinear phase noise

Phase-preserving amplitude regeneration of a two-amplitude-level modulation format - Röthlingshöfer, Tobias; Richter, Thomas; Schubert, Colja; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Conference on Lasers and Electro-Optics Pacific Rim, 2013)
It has been experimentally shown that a modified nonlinear loop mirror can be used for all-optical star8-QAM processing. An amplitude noise reduction of 2.2 dB could be demonstrated for the high-power state
lhft_intern.bib::Roethlingshoefer2013b

Phase-Preserving Amplitude Regeneration Using Dispersion-Imbalanced Loop Mirror - Röthlingshöfer, Tobias; Sponsel, Klaus; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Optical Fiber Communication 2009, 2009)
Scheme and parameters of dispersion-imbalance loop mirror (DILM) have been optimized for phase-preserving amplitude 2R regeneration. DILM performance for DPSK transmission has been evaluated in numerical simulations. A 4.8 dB Q-factor improvement has been demonstrated. © 2009 OSA.
UnivIS-Import:2017-12-18:Pub.2009.tech.IE.LEH.phasep
Keywords: (060.4370) Nonlinear optics; fibers; (060.5060) Phase modulation

Phase-Preserving Multilevel Amplitude Regeneration Using a Modified Nonlinear Amplifying Loop Mirror - Hierold, M.; Roethlingshoefer, T.; Sponsel, K.; Onishchukov, G.; Schmauß, Bernhard; Leuchs, Gerd (12th International Conf. on Digital Object Identifier (ICTON), Munich, June, 2010)
lhft_intern.bib::Hierold10

Phase-Preserving Signal Regeneration by a Nonlinear Amplifying Loop Mirror - Sponsel, Klaus; Cvecek, Kristian; Stephan, Christian; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Cleo Juni, 2007)
This work presents the numerical investigations on the physical limitations and optimization of the nonlinear amplifying loop mirror (NALM) as a regenerator of phase-shift-keyed signals. The NALM consists of a bidirectional amplifier and a highly nonlinear fiber (HNLF), combined to a loop by a fiber coupler. The transfer functions for the NALM versus dispersion for an amplifier gain for anomalous and normal dispersion were studied. It should be mentioned that beside the nonlinear chirp, the NALM also causes spectral broadening and pulse shape distortions. Amplified spontaneous emission from the NALM amplifier is comparably lower and therefore negligible as a source of optical signal-to-noise ratio (OSNR) penalty.
UnivIS-Import:2017-12-18:Pub.2007.tech.IE.LEH.phasep_0

Phase regeneration of a star-8QAM signal in a phase-sensitive amplifier with conjugated pumps - Stiller, Birgit; Onishchukov, Georgy; Schmauß, Bernhard; Leuchs, Gerd (Optics Express, 2014)
We demonstrate numerically phase regeneration of a star-8QAM signal with two amplitude and four phase states in a phase-sensitive amplifier. In a dual-stage setup, two phase-conjugated idlers are generated in a first stage consisting of two fiber-optic parametric phase-insensitive amplifiers operated in highly nonlinear gain regime. These are used as pumps in the second, phase-sensitive amplification stage which enables efficient phase regeneration via a degenerate four-wave-mixing process. The latter can be operated in two different operation modes: without format conversion or with phase-shifted amplitude levels. In both regimes, we observe high phase-regeneration efficiency for all amplitude levels: the initial phase noise with 0.2 rad standard deviation is reduced by a factor of 5.
lhft_intern.bib::Stiller2014

Phase retrieval from carrier frequency interferograms: reduction of the impact of space-variant disturbances - Schwider, Johannes; Nercissian, Vanusch; Mantel, Klaus Peter (Journal of the European Optical Society: Rapid Publications, 2015)

Phase-shift extraction for generalized phase-shifting interferometry - Peng, Gao; Yao, Baoli; Lindlein, Norbert; Mantel, Klaus Peter; Harder, Irina; Geist, Eduard (Optics Letters, 2009)
A simple algorithm for blind extraction of phase shifts is proposed for generalized phase-shifting interferometry from only three interferograms. Based on the statistical property of the object wave, the algorithm calculates approximately the involved phase shifts as initial values. The extraction is further improved by an iterative method, considering the fact that the closer the phase shifts approach their real values, the more uniform the reconstructed reference wave will become. The feasibility of this algorithm is demonstrated by both simulation and experiment. © 2009 Optical Society of America.
UnivIS-Import:2015-04-14:Pub.2009.nat.dphy.optik.1optik.phases

Phase-shifting point-diffraction interferometry with common-path and in-line configuration for microscopy - Peng, Gao; Harder, Irina; Nercissian, Vanusch; Mantel, Klaus; Yao, Baoli (Optics Letters, 2010)

Phase-shifting Zernike phase contrast microscopy for quantitative phase measurement - Peng, Gao; Yao, Baoli; Harder, Irina; Lindlein, Norbert; Torcall-Milla, Francisco Jose (Optics Letters, 2011)

Phase singularity reduction in speckle interferometry by tailoring the spatial coherence of light - Mantel, K.; Barakat, Ismail; Nercissian, Vanusch; Harder, I.; Rothau, S. (Applied Optics, 2021)
Reducing the number of phase singularities in speckle interferometry by physical means increases the quality of the phase deconvolution and enhances the separability of fringe systems, especially for highly dynamic fringe systems. The reduction is achieved by tailoring the spatial coherence of the light source at the entrance of the interferometer. The reduction mechanism is non-intuitive and rests on a change of size and of position of the speckle patterns as a result of the spatially shaped coherence. After demonstrating the amount of reduction that may be achieved, the reduction mechanism is explained theoretically and via simulations, and it is vindicated in an experiment using a Michelson-Mach-Zehnder interferometer hybrid.
CRIS-Team Scopus Importer:2021-08-20

Phenomena induced by photoionisation in gas-filled hollow-core photonic crystal fibres - Tani, Francesco; Köhler, Johannes; Suresh, Mallika; Schade, Daniel; Köttig, Felix; Russell, Philip St. John (International Conference on Transparent Optical Networks, 2020)
The optical properties of hollow-core photonic crystal fibre (HC-PCF) can be conveniently tailored by modifying the transverse microstructure and selecting the species and pressure of the gas filling the hollow regions. Additionally, absorption of light by the gas can result in transient changes in refractive index, with characteristic timescales varying from a few hundred femtoseconds to hundreds of microseconds. Understanding the dynamics of these effects is essential for scaling the power and the repetition rate of laser pulse trains launched into HC-PCF, is relevant for pump-probe experiments, and can suggest new ways of controlling the guiding properties of these fibres. Here we review our recent studies, showing measurements of the temporal evolution of local changes in refractive index and describing the novel experimental techniques we developed to investigate the effects.
CRIS-Team Scopus Importer:2020-10-23
Keywords: Nonlinear optics; Photonic crystal fibres

Photochemical Microreactors in Photonic Crystal Fibers - Cubillas, Ana Maria; Scharrer, Michael; Euser, Tijmen G.; Schmidt, Matthias; Etzold, Bastian; Taccardi, Nicola; Wasserscheid, Peter; Russell, Philip St. John (OSA Publishing, 2012)
Hollow-core photonic crystal fiber offers new possibilities for sensing and photochemistry applications. In this paper we review our recent achievements on liquid-phase photochemical microreactors using photonic crystal fibers and discuss our future prospects in this field.

Photochemistry in a soft-glass single-ring hollow-core photonic crystal fibre - Cubillas, Ana M.; Jiang, Xin; Euser, Tijmen G.; Taccardi, Nicola; Etzold, Bastian; Wasserscheid, Peter; Russell, Philip St. John (Analyst, 2017)
A hollow-core photonic crystal fibre (HC-PCF), guided by photonic bandgap effects or anti-resonant reflection, offers strong light confinement and long photochemical interaction lengths in a microscale channel filled with a solvent of refractive index lower than that of glass (usually fused silica). These unique advantages have motivated its recent use as a highly efficient and versatile microreactor for liquid-phase photochemistry and catalysis. In this work, we use a single-ring HC-PCF made from a high-index soft glass, thus enabling photochemical experiments in higher index solvents. The optimized light-matter interaction in the fibre is used to strongly enhance the reaction rate in a proof-of-principle photolysis reaction in toluene.
EAM Import::2019-03-12

Photochemistry in hollow-core photonic crystal fiber microreactors - Euser, Tijmen G.; Cubillas, Ana Maria; Jiang, X.; Unterkofler, Sarah; Etzold, Bastian; Wasserscheid, Peter; Jones, Anita C.; Sadler, Peter J.; Russell, Philip St. John (Laser Applications to Chemical, Security and Environmental Analysis, 2014)
Hollow-core photonic crystal fiber uniquely allows low-loss propagation of light in liquid-filled microchannels, thus enabling highly efficient photochemistry, photo-switching, and photocatalysis at optical powers that are five orders of magnitude lower than in conventional systems.

Photochemistry in Photonic Crystal Fiber Nanoreactors - Chen, Jocelyn S. Y.; Euser, Tijmen G.; Farrer, Nicola J.; Sadler, Peter J.; Scharrer, Michael; Russell, Philip St. John (Chemistry - A European Journal, 2010)
We report the use of a liquid-filled hollow-core photonic crystal fiber (PCF) as a highly controlled photochemical reactor. Hollow-core PCFs have several major advantages over conventional sample cells: the sample volume per optical path length is very small (2.8nL cm-1 in the fiber used), long optical path lengths are possible as a result of very low intrinsic waveguide loss, and furthermore the light travels in a diffractionless single mode with a constant transverse intensity profile. As a proof of principle, the (very low) quantum yield of the photochemical conversion of vitamin B12, cyanocobalamin (CNCbl) to hydroxocobalamin ([H_2OCbl]+) in aqueous solution was measured for several pH values from 2.5 to 7.5. The dynamics of the actively induced reaction were monitored in real-time by broadband absorption spectroscopy. The PCF nanoreactor required ten thousand times less sample volume compared to conventional techniques. Furthermore, the enhanced sensitivity and optical pump intensity implied that even systems with very small quantum yields can be measured very quickly—in our experiments one thousand times faster than in a conventional cuvette.
EAM Import::2019-03-12

Photochemistry on soft-glass hollow-core photonic crystal fibre - Cubillas, Ana Maria; Jiang, X.; Euser, Tijmen G.; Taccardi, Nicola; Etzold, Bastian; Wasserscheid, Peter; Russell, Philip St. John (23rd International Conference on Optical Fibre Sensors, 2014)
Hollow-core photonic crystal fibre (HC-PCF) offers strong light confinement and long interaction lengths in an optofluidic channel. These unique advantages have motivated its recent use as a highly efficient and versatile microreactor for liquid-phase photochemistry and catalysis. In this work, we use a soft-glass HC-PCF to carry out photochemical experiments in a high-index solvent such as toluene. The high-intensity and strong confinement in the fibre is demonstrated to enhance the performance of a proof-of-principle photolysis reaction.

Photon bunching reveals single-electron cathodoluminescence excitation efficiency in InGaN quantum wells - Meuret, Sophie; Coenen, Toon; Zeijlemaker, Hans; Latzel, Michael; Christiansen, Silke; Conesa-Boj, Sonia; Polman, Albert (Physical Review B, 2017)
Cathodoluminescence spectroscopy is a key analysis technique in nanophotonics research and technology, yet many aspects of its fundamental excitation mechanisms are not well understood on the single-electron and single-photon level. Here, we determine the cathodoluminescence emission statistics of InGaN quantum wells embedded in GaN under 6–30-keV electron excitation and find that the light emission rate varies strongly from electron to electron. Strong photon bunching is observed for the InGaN quantum well emission at 2.77 eV due to the generation of multiple quantum well excitations by a single primary electron. The bunching effect, measured by the g(2)(t) autocorrelation function, decreases with increasing beam current in the range 3–350 pA. Under pulsed excitation (p=2–100ns; 0.13–6 electrons per pulse), the bunching effect strongly increases. A model based on Monte Carlo simulations is developed that assumes a fraction extgreekg of the primary electrons generates electron-hole pairs that create multiple photons in the quantum wells. At a fixed primary electron energy (10 keV) the model explains all g(2) measurements for different beam currents and pulse durations using a single value for extgreekg=0.5. At lower energies, when electrons cause mostly near-surface excitations, extgreekg is reduced ( extgreekg=0.01 at 6 keV), which is explained by the presence of a AlGaN barrier layer that inhibits carrier diffusion to the buried quantum wells. The combination of g(2) measurements in pulsed and continuous mode with spectral analysis provides a powerful tool to study optoelectronic properties and may find application in many other optically active systems and devices.
EAM Import::2019-03-12