Light scattering from laser pulseinduced travelling inhomogeneities
T. Roger, E. Rubino, S. Cacciatori, F. Belgiorno, F. Biancalana, M. F. Saleh, A. Couairon, D. Faccio
Conference on Lasers and ElectroOptics
(2013)
Light scattering from a Kerr induced inhomogeneity is revisited, unveiling novel emission channels resulting essentially from the formation of shock front instabilities. These exhibit different features in the presence of negative or positive GVD. (C) 2013 Optical Society of America
Interaction between optical fields and their conjugates in nonlinear
media
Motivated by recent experimental results, we demonstrate that the ubiquitous pulse propagation equation based on a single generalized nonlinear Schrodinger equation is incomplete and inadequate to explain the formation of the so called negativefrequency resonant radiation emitted by optical solitons. The origin of this deficiency is due to the absence of a peculiar nonlinear coupling between the positive and negative frequency components of the pulse spectrum during propagation, a feature that the slowlyvarying envelope approximation is unable to capture. We therefore introduce a conceptually new model, based on the envelope of the analytic signal, that takes into account the full spectral dynamics of all frequency components, is prone to analytical treatment and retains the simulation efficiency of the nonlinear Schrodinger equation. We use our new equation to derive from first principles the phasematching condition of the negativefrequency resonant radiation observed in previously reported experiments. (C) 2013 Optical Society of America
DNA hybridization assay at individual, biofunctionalized zinc oxide
nanowires
Christian Leiterer, Barbara Seise, Irma Slowik, Gerald Broenstrup, Raphael Niepelt, Karina Weber, Carsten Ronning, Silke Christiansen, Wolfgang Fritzsche
JOURNAL OF BIOPHOTONICS
6(2)
143147
(2013)

Journal
Reliable and efficient identification of DNA is a major goal in onsite diagnostics. One dimensional nanostructures like nanowires (NW) represent potential sensor structures due to their extreme surfacetobulk ratio, enabling enhanced biomolecule binding which results in optimal signals. While silicon NW are already well studied, NW made from other materials with promising properties like ZnO are not yet established as NW sensor material for bioanalytics. Here we demonstrate the DNA functionalization of ZnO NW even at the single NW level and their successful application in a DNA hybridization assay. ((c) 2013 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim)
The polarization properties of a tilted polarizer
Jan Korger, Tobias Kolb, Peter Banzer, Andrea Aiello, Christoffer Wittmann, Christoph Marquardt, Gerd Leuchs
Polarizers are key components in optical science and technology. Thus, understanding the action of a polarizer beyond oversimplifying approximations is crucial. In this work, we study the interaction of a polarizing interface with an obliquely incident wave experimentally. To this end, a set of Mueller matrices is acquired employing a novel procedure robust against experimental imperfections. We connect our observation to a geometric model, useful to predict the effect of polarizers on complex light fields. (C) 2013 Optical Society of America
Quantum key distribution  vulnerable if imperfectly implemented
G. Leuchs
Proceedings of SPIE
8899
UNSP 88990L
(2013)

Journal
We report several vulnerabilities found in Clavis2, the flagship quantum key distribution (QKD) system from ID Quantique. We show the hacking of a calibration sequence run by Clavis2 to synchronize the Alice and Bob devices before performing the secret key exchange. This hack induces a temporal detection efficiency mismatch in Bob that can allow Eve to break the security of the cryptosystem using faked states. We also experimentally investigate the superlinear behaviour in the singlephoton detectors (SPDs) used by Bob. Due to this superlinearity, the SPDs feature an actual multiphoton detection probability which is generally higher than the theoreticallymodelled value. We show how this increases the risk of detector control attacks on QKD systems (including Clavis2) employing such SPDs Finally, we review the experimental feasibility of Trojanhorse attacks. In the case of Clavis2, the objective is to read Bob's phase modulator to acquire knowledge of his basis choice as this information suffices for constructing the raw key in the ScaraniAcinRibordyGisin 2004 (SARG04) protocol. We work in close collaboration with ID Quantique and for all these loopholes, we notified them in advance. Wherever possible, we or ID Quantique proposed countermeasures and they implemented suitable patches and upgrade their systems.
Orbital angular momentum from marginals of quadrature distributions
L. L. SanchezSoto, A. B. Klimov, P. de la Hoz, I. Rigas, J. Rehacek, Z. Hradil, G. Leuchs
We set forth a method to analyze the orbital angular momentum of a light field. Instead of using the canonical formalism for the conjugate pair angleangular momentum, we model this latter variable by the superposition of two independent harmonic oscillators along two orthogonal axes. By describing each oscillator by a standard Wigner function, we derive, via a consistent change of variables, a comprehensive picture of the orbital angular momentum. We compare this with previous approaches and show how this method works in some relevant examples.
Solitonradiation trapping in gasfilled hollowcore photonic crystal
fibers
Mohammed F. Saleh, Fabio Biancalana
Conference on Lasers and ElectroOptics
(2013)
We propose an unconventional optical trapping mechanism between a strong fundamental soliton and an ultrashort weak dispersive radiation in a hollowcore photonic crystal fiber filled by a noble gas.
A TimeResolved Numerical Study of the VaporLiquidSolid Growth
Kinetics Describing the Initial Nucleation Phase as well as Pulsed
Deposition Processes
Bjoern Eisenhawer, Vladimir Sivakov, Silke Christiansen, Fritz Falk
Today, the vapor liquid solid (VLS) growth mechanism is a common process for the metal catalyzed bottomup growth of semiconductor nanowires (NWs). Nevertheless, most of the literature only is concerned with the steadystate NW growth which applies when the amount of material supplied is equal to the amount consumed by the NW growth at the same time. While this description is suitable for chemical vapor deposition (CVD) or electron beam evaporation (EBE) processes after the initial nucleation time, problems arise when pulsed growth processes like pulsed laser deposition (PLD) are used since in this case the steady state growth condition cannot be applied. Moreover, the initial phase of NW growth cannot be described with steady state growth conditions, either. In this work, we present a modeling approach for VLS NW growth based on numerical simulations, which is capable of describing the nucleation phase of the VLS growth process as well as a pulsed deposition process.
A sum rule for charged elementary particles
Gerd Leuchs, Luis L. SanchezSoto
EUROPEAN PHYSICAL JOURNAL D
67(3)
57
(2013)

Journal
There may be a link between the quantum properties of the vacuum and the parameters describing the properties of light propagation, culminating in a sum over all types of elementary particles existing in Nature weighted only by their squared charges and independent of their masses. The estimate for that sum is of the order of 100.
The Schmidt modes of biphoton qutrits: Poincaresphere representation
M. V. Chekhova, M. V. Fedorov
JOURNAL OF PHYSICS BATOMIC MOLECULAR AND OPTICAL PHYSICS
46(9)
095502
(2013)

Journal
For a generalform polarization biphoton qutrit, physically corresponding to a pair of arbitrarily polarized photons in a single frequency and wavevector mode, we explicitly find polarization Schmidt modes. A simple method is suggested for factorizing the state vector and the explicit expressions for the factorizing photon creation operators are found. The degrees of entanglement and polarization of a qutrit are shown to depend directly on the commutation features of the factorizing operators. Clear graphic representations for the Stokes vectors of the qutrit state as a whole, its Schmidt modes and factorizing singlephoton creation operators are given based on the Poincare sphere. An experimental scheme is proposed for measuring the parameters of the Schmidt decomposition as well as for demonstrating the operational meaning of qutrit entanglement.
Transverse Entanglement of Biphotons
Felix Just, Andrea Cavanna, Maria V. Chekhova, Gerd Leuchs
Conference on Lasers and ElectroOptics
(2013)
We study the transverse entanglement of biphotons generated via parametric downconversion as they propagate from the near to the far field. We obtain the Fedorov ratio and the Schmidt number and compare the results. (C) 2013 Optical Society of America
GoosHanchen and ImbertFedorov shifts from a quantummechanical
perspective
We study the classical optics effects known as GoosHanchen and ImbertFedorov shifts, occurring when reflecting a bounded light beam from a planar surface, by using a quantummechanical formalism. This new approach allows us to naturally separate the spatial shift into two parts, one independent on orbital angular momentum (OAM) and the other one showing OAMinduced spatialversusangular shift mixing. In addition, within this quantummechanicallike formalism, it becomes apparent that the angular shift is proportional to the beams angular spread, namely to the variance of the transverse components of the wave vector. Moreover, we extend our treatment to the enhancement of beam shifts via weak measurements and relate our results to the recent experiments.
Mode structure and polaritonic contributions to the Casimir effect in a
magnetodielectric cavity
We present a full analysis of the mode spectrum in a cavity formed by two parallel plates, one of which is magnetodielectric (metamaterial) while the other one is metallic, and obtain dispersion relations in closed form. The optical properties of the cavity walls are described in terms of realistic models for effective permittivity and permeability. Surface polaritons, i.e., electromagnetic modes that have at least partly an evanescent character, are shown to dominate the Casimir interaction at small separations. We analyze in detail the spolarized polaritons, which are a characteristic feature of a magnetodielectric configuration, and discuss their role in the repulsive Casimir force.
Effects of squeezedfilm damping on the optomechanical nonlinearity in
dualnanoweb fiber
J. R. Koehler, A. Butsch, T. G. Euser, R. E. Noskov, P. St. J. Russell
The freelysuspended glass membranes in a dualnanoweb fiber, driven at resonance by intensitymodulated light, exhibit a giant optomechanical nonlinearity. We experimentally investigate the effect of squeezedfilm damping by exploring the pressure dependence of resonant frequency and mechanical quality factor. As a consequence of the unusually narrow slot between the nanowebs (22 mu m by 550nm), the gasspring effect causes a pressuredependent frequency shift that is similar to 15 times greater than typically measured in microelectromechanical devices. When evacuated, the dualnanoweb fiber yields a quality factor of similar to 3 600 and a resonant optomechanical nonlinear coefficient that is similar to 60 000 times larger than the Kerr effect. (C) 2013 AIP Publishing LLC.
Directional emission of dielectric disks with a finite scatterer in the
THz regime
S. Preu, S. I. Schmid, F. Sedlmeir, J. Evers, H. G. L. Schwefel
In the Terahertz (THz) domain, we investigate both numerically and experimentally the directional emission of whispering gallery mode resonators that are perturbed by a small scatterer in the vicinity of the resonators rim. We determine quality factor degradation, the modal structure and the emission direction for various geometries. We find that scatterers do allow for directional emission without destroying the resonator's quality factor. This finding allows for new geometries and outcoupling scenarios for active whispering gallery mode structures such as quantum cascade lasers and passive resonators such as evanescent sensors. The experimental results agree well with finite difference time domain simulations. (C) 2013 Optical Society of America
Terahertz relativistic spatial solitons in doped graphene metamaterials
H. Dong, C. Conti, A. Marini, F. Biancalana
JOURNAL OF PHYSICS BATOMIC MOLECULAR AND OPTICAL PHYSICS
46(15)
155401
(2013)

Journal
We propose an electrically tunable graphenebased metamaterial that shows a large nonlinear optical response at THz frequencies. The responsible nonlinearity comes from the intraband current, which we are able to calculate analytically. We demonstrate that the proposed metamaterial supports stable 2D spatial solitary waves. Our theoretical approach is not restricted to graphene, but can be applied to all materials exhibiting a conical dispersion supporting massless Dirac fermions.
We measure the transverse entanglement of photon pairs on their propagation from the near to the far field of spontaneous parametric downconversion (SPDC). The Fedorov ratio, depending on the widths of conditional and unconditional intensity measurements, is shown to be only able to characterize entanglement in the near and far field zones of the source. Therefore we also follow a different approach. By evaluating the firstorder coherence of a subsystem of the state we can quantify its entanglement. Unlike previous measurements, which determine the Fedorov ratio via intensity correlations, our setup is sensitive to both phase and modulus of the biphoton state and thus always grants experimental access to the full transverse entanglement of the SPDC state. It is shown theoretically that this scheme represents a direct measurement of the Schmidt number.
Determination of the effective refractive index of nanoparticulate ITO
layers
M. Baum, I. Alexeev, M. Latzel, S. H. Christiansen, M. Schmidt
Nanoparticles of transparent conducting oxides, such as indium tin oxide, can be used in printing techniques to generate functional layers for various optoelectronic devices. Since these deposition methods do not create fully consolidated films, the optical properties of such layers are expected to be notably different from those of the bulk material and should be characterized on their own. In this work we present a way to measure the effective refractive index of a particulate ITO layer by refraction of light. The obtained data points are used to identify an accurate layer model for spectroscopic ellipsometry. In this way the complex refractive index of the particle layer is determined in a wide spectral range from ultra violet to near infrared. (c) 2013 Optical Society of America
HighTg TOPAS microstructured polymer optical fiber for fiber Bragg
grating strain sensing at 110 degrees
Christos Markos, Alessio Stefani, Kristian Nielsen, Henrik K. Rasmussen, Wu Yuan, Ole Bang
We present the fabrication and characterization of fiber Bragg gratings (FBGs) in an endlessly singlemode microstructured polymer optical fiber (mPOF) made of humidityinsensitive highTg TOPAS cyclic olefin copolymer. The mPOF is the first made from grade 5013 TOPAS with a glass transition temperature of Tg = 135 degrees C and we experimentally demonstrate high strain operation (2.5%) of the FBG at 98 degrees C and stable operation up to a record high temperature of 110 degrees C. The Bragg wavelengths of the FBGs are around 860 nm, where the propagation loss is 5.1dB/m, close to the fiber loss minimum of 3.67dB/m at 787nm. (C) 2013 Optical Society of America
Nonlinear amplification of sidemodes in frequency combs
R. A. Probst, T. Steinmetz, T. Wilken, H. Hundertmark, S. P. Stark, G. K. L. Wong, P. St. J. Russell, T. W. Haensch, R. Holzwarth, Th. Udem, et al.
We investigate how suppressed modes in frequency combs are modified upon frequency doubling and selfphase modulation. We find, both experimentally and by using a simplified model, that these sidemodes are amplified relative to the principal comb modes. Whereas frequency doubling increases their relative strength by 6 dB, the growth due to selfphase modulation can be much stronger and generally increases with nonlinear propagation length. Upper limits for this effect are derived in this work. This behavior has implications for highprecision calibration of spectrographs with frequency combs used for example in astronomy. For this application, FabryPerot filter cavities are used to increase the mode spacing to exceed the resolution of the spectrograph. Frequency conversion and/or spectral broadening after nonperfect filtering reamplify the suppressed modes, which can lead to calibration errors. (C) 2013 Optical Society of America
Coherent Interaction of Light with a Metallic Structure Coupled to a
Single Quantum Emitter: From Superabsorption to Cloaking
We provide a general theoretical platform based on quantized radiation in absorptive and inhomogeneous media for investigating the coherent interaction of light with material structures in the immediate vicinity of quantum emitters. In the case of a very small metallic cluster, we demonstrate extreme regimes where a single emitter can either counteract or enhance particle absorption by 3 orders of magnitude. For larger structures, we show that an emitter can eliminate both scattering and absorption and cloak a plasmonic antenna. We provide physical interpretations of our results and discuss their applications in active metamaterials and quantum plasmonics. DOI: 10.1103/PhysRevLett.110.153605
Coherent scattering from aligned single quantum emitters in a dielectric
nanoguide
S. Faez, P. Tuerschmann, S. Goetzinger, V. Sandoghdar
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Optomechanical and optoacoustic phenomena in microstructured silica
fibres
A. Butsch, M. S. Kang, T. G. Euser, P. St J. Russell
Recent results on optomechanical and optoacoustic nonlinearities in optical fibres are reported. In a new type of a microstructured silica fibre, comprising two ultrathin closely spaced glass waveguides, an extremely high and optically broadband optomechanical nonlinearity is shown to occur. This nonlinearity originates from the optical gradient forces between coupled waveguides, can exceed the Kerr effect by many orders of magnitude and allows the formation of stable selftrapped optical modes that represent a novel kind of optical soliton. Furthermore, optoacoustic interaction via electrostriction in the micronsized core of a photonic crystal fibre is studied. It is demonstrated, that coherent opticallydriven acoustic waves, tightly guided in the core, can facilitate infibre dynamic optical isolation and alloptical switching.
Growth of GaN Nanorods and Wires and Spectral Tuning of Whispering
Gallery Modes in Tapered GaN Wires
Christian Tessarek, Christel Dieker, Erdmann Spiecker, Silke Christiansen
JAPANESE JOURNAL OF APPLIED PHYSICS
52(8)
UNSP 08JE09
(2013)

Journal
This paper reports on the growth of GaN nanorods and wires by metalorganic vapor phase epitaxy. Density, height and diameter are strongly influenced by the growth time. A deposition time of a few minutes leads to the formation of GaN nanorods. Increasing the deposition time up to 1 h yields wires with heights exceeding 47 mu m. Transmission electron microscopy and convergent beam electron diffraction measurements are showing the presence of N and Gapolar GaN in a single nanorod. Cathodoluminescence measurements are performed showing the appearance of whispering gallery modes. Due to slight tapering of the wires the whispering gallery modes can be spectrally tuned by changing the position of the exposing electron beam at the sidewall facet of the rod. (C) 2013 The Japan Society of Applied Physics
Deeply subwavelength SPP components for nanophotonic circuitry
A. Kriesch, S. P. Burgos, D. Ploss, Hannes Pfeifer, H. A. Atwater, U. Peschel
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Vector modulational instability induced by parametric resonance in
periodically tapered highly birefringent optical fibers
We study the modulational instability induced by periodic variations of groupvelocity dispersion and nonlinear coefficients in a highly birefringent fiber. We observe, for each resonance order, the presence of two pairs of genuine vectortype sidebands, which are spectrally unbalanced between the polarization components for nonzero groupindex mismatch, and one pair of balanced sidebands emerging and dominating at increasing groupindex mismatch. As the conventional modulational instabilitymanifests itself, it is partially suppressed by the proximity of these additional unstable regions.
An optimized photon pair source for quantum circuits
Georg Harder, Vahid Ansari, Benjamin Brecht, Thomas Dirmeier, Christoph Marquardt, Christine Silberhorn
We implement an ultrafast pulsed typeII parametric down conversion source in a periodically poled KTP waveguide at telecommunication wavelengths with almost identical properties between signal and idler. As such, our source resembles closely a pure, genuine single mode photon pair source with indistinguishable modes. We measure the joint spectral intensity distribution and second order correlation functions of the marginal beams and find with both methods very low effective mode numbers corresponding to a Schmidt number below 1.16. We further demonstrate the indistinguishability as well as the purity of signal and idler photons by HongOuMandel interferences between signal and idler and between signal/idler and a coherent field, respectively. Without using narrowband spectral filtering, we achieve a visibility for the interference between signal and idler of 94.8% and determine a purity of more than 80% for the heralded single photon states. Moreover, we measure raw heralding efficiencies of 20.5% and 15.5% for the signal and idler beams corresponding to detectorloss corrected values of 80% and 70%. (C) 2013 Optical Society of America
Semianalytical model for the evolution of femtosecond pulses during
supercontinuum generation in synchronously pumped ring cavities
M. J. Schmidberger, F. Biancalana, P. St J. Russell, N. Y. Joly
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
SCATTERING OF AN EXPONENTIAL PULSE BY A SINGLE ATOM
Markus Sondermann, Gerd Leuchs
ROMANIAN REPORTS IN PHYSICS
65(3)
638645
(2013)
We discuss the scattering of a light pulse by a single atom in free space using a purely semiclassical framework. The atom is treated as a linear elastic scatterer allowing to treat each spectral component of the incident pulse separately. For an increasing exponential pulse with a dipole radiation pattern incident from full solid angle the spectrum resulting from interference of incident and scattered components is a decreasing exponential pulse.*
Performance of scientific cameras with different sensor types in
measuring dynamic processes in fluorescence microscopy
Jasmin Jung, Siegfried Weisenburger, Sahradha Albert, Daniel F. Gilbert, Oliver Friedrich, Volker Eulenburg, Johannes Kornhuber, Teja W. Groemer
MICROSCOPY RESEARCH AND TECHNIQUE
76(8)
835843
(2013)

Journal
The plethora of available scientific cameras of different types challenges the biologically oriented experimenter when picking the appropriate camera for his experiment. In this study, we chose to investigate camera performances in a typical nonsingle molecule situation in life sciences, that is, quantitative measurements of fluorescence intensity changes from video data with typically skewed intensity distributions. Here, intensity profile dynamics of pHsensors upon triggered changes of pHenvironments in living cells served as a model system. The following camera types were tested: sCMOS, CCD (scientific and nonscientific) and EMCCD (backand frontilluminated). We found that although the EMCCD cameras achieved the best absolute spatial SNR (signaltonoise ratio) values, the sCMOS was at least of equal performance when the spatial SNR was related to the effective dynamic range, and it was superior in terms of temporal SNR. In the measurements of triggered intensity changes, the sCMOS camera had the advantage that it used the smallest fraction of its dynamic range when depicting intensity changes, and thus featured the best SNR at full usage of its dynamic range. (C) 2013 Wiley Periodicals, Inc.
Close to threeoctavespanning supercontinuum generated in ZBLAN photonic crystal fiber
Xin Jiang, Nicolas Y. Joly, Martin A. Finger, Gordon K. L. Wong, Fehim Babic, M. Saad, Philip St. J. Russell
Advanced Solid State Lasers [Postdeadline Papers (JTh5A)]
(2013)

Journal
We report the successful fabrication of a ZBLAN photonic crystal fiber with submicron features and large airfilling fraction and use it to generate a 10dBflat supercontinuum (350 to 2500nm) from 140fs, 1nJ pulses at 1042nm.
Detection of Single Nanoparticles and Lentiviruses Using Microcavity
Resonance Broadening
Linbo Shao, XueFeng Jiang, XiaoChong Yu, BeiBei Li, William R. Clements, Frank Vollmer, Wei Wang, YunFeng Xiao, Qihuang Gong
A new labelfree sensing mechanism is demonstrated experimentally by monitoring the whisperinggallery mode broadening in microcavities. It is immune to both noise from the probe laser and environmental disturbances, and is able to remove the strict requirement for ultrahighQ mode cavities for sensitive nanoparticle detection. This ability to sense nanoscale objects and biological analytes is particularly crucial for wide applications.
GoosHanchen and ImbertFedorov shifts for bounded wavepackets of light
We present precise expressions for the spatial and angular GoosHanchen and ImbertFedorov shifts experienced by a longitudinally and transversally limited beam of light (wavepacket) upon reflection from a dielectric interface, as opposed to the wellknown case of a monochromatic beam which is bounded in transverse directions but infinitely extended along the direction of propagation. This is done under the assumption that the detector time is longer than the temporal length of the wavepacket (wavepacket regime). Our results will be applied to the case of a Gaussian wavepacket and show that, at the leading order in the Taylor expansion of reflected field amplitudes, the results are the same as in the monochromatic case.
Distributing Entanglement with Separable States
Christian Peuntinger, Vanessa Chille, Ladislav Mista Jr., Natalia Korolkova, Michael Foertsch, Jan Korger, Christoph Marquardt, Gerd Leuchs
We experimentally demonstrate a protocol for entanglement distribution by a separable quantum system. In our experiment, two spatially separated modes of an electromagnetic field get entangled by local operations, classical communication, and transmission of a correlated but separable mode between them. This highlights the utility of quantum correlations beyond entanglement for the establishment of a fundamental quantum information resource and verifies that its distribution by a dual classical and separable quantum communication is possible.
Topological Zeeman effect and circular birefringence in twisted photonic
crystal fibers
T. Weiss, G. K. L. Wong, F. Biancalana, S. M. Barnett, X. M. Xi, P. St. J. Russell
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA BOPTICAL PHYSICS
30(11)
29212927
(2013)

Journal
The propagation of light guided in optical fibers is affected in different ways by bending or twisting. Here we treat the polarization properties of twisted sixfold symmetric photonic crystal fibers. Using a coordinate frame that follows the twisting structure, we show that the governing equation for the fiber modes resembles the Pauli equation for electrons in weak magnetic fields. This implies index splitting between left and right circularly polarized modes, which are degenerate in the untwisted fiber. We develop a theoretical model, based on perturbation theory and symmetry properties, to predict the observable circular birefringence (i.e., optical activity) associated with this splitting. Our overall conclusion is that optical activity requires the rotational symmetry to be broken so as to allow coupling between different total angular momentum states. (C) 2013 Optical Society of America
Nonlinear optics in hollow core PCF filled with gaseous and
supercritical xenon
M. Azhar, N. Y. Joly, J. C. Travers, F. Tani, P. St J. Russell
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Compensation of anisotropy effects in a nonlinear crystal for squeezed
vacuum generation
A. M. Perez, F. Just, A. Cavanna, M. V. Chekhova, G. Leuchs
Squeezed vacuum can be obtained by an optical parametric amplifier (OPA) with the quantum vacuum state at the input. We are interested in a degenerate typeI OPA based on parametric downconversion (PDC) where, due to phase matching requirements, an extraordinary polarized pump must impinge onto a birefringent crystal with a large chi((2)) nonlinearity. As a consequence of the optical anisotropy of the medium, the spatial spectrum of the generated radiation is affected by the transverse walkoff. In this work we describe a method that reduces the spatial distortions, by using two consecutive crystals instead of one. We show that after anisotropy compensation the twophoton amplitude becomes symmetric, allowing for a simple Schmidt expansion, a procedure that in practice requires states that come from experimental systems free of anisotropy effects. Qualitative experimental observations are made for the case of highgain PDC.
Modebased microparticle conveyor belt in airfilled hollowcore
photonic crystal fiber
Oliver A. Schmidt, Tijmen G. Euser, Philip St. J. Russell
We show how microparticles can be moved over long distances and precisely positioned in a lowloss airfilled hollowcore photonic crystal fiber using a coherent superposition of two copropagating spatial modes, balanced by a backwardpropagating fundamental mode. This creates a series of trapping positions spaced by half the beatlength between the forwardpropagating modes (typically a fraction of a millimeter). The system allows a trapped microparticle to be moved along the fiber by continuously tuning the relative phase between the two forwardpropagating modes. This modebased optical conveyor belt combines longrange transport of microparticles with a positional accuracy of 1 mu m. The technique also has potential uses in waveguidebased optofluidic systems. (C)2013 Optical Society of America
Full Solid Angle IonLight Interface
Martin Fischer, Robert Maiwald, Andrea Golla, Marianne Bader, Markus Sondermann, Gerd Leuchs
Conference on Lasers and ElectroOptics
(2013)
We present an optical system covering 81 % of the solid angle into which an ion emits light. With this configuration we focus light close to the diffraction limit, while also approaching optimal light matter coupling. (C) 2013 Optical Society of America
Optomechanically Induced Transparency in the Nonlinear Quantum Regime
Andreas Kronwald, Florian Marquardt
PHYSICAL REVIEW LETTERS
111(13)
133601
(2013)

Journal

PDF
Optomechanical systems have been shown both theoretically and experimentally to exhibit an analogon to atomic electromagnetically induced transparency, with sharp transmission features that are controlled by a second laser beam. Here we investigate these effects in the regime where the fundamental nonlinear nature of the optomechanical interaction becomes important. We demonstrate that pulsed transistorlike switching of transmission still works even in this regime. We also show that optomechanically induced transparency at the second mechanical sideband could be a sensitive tool to see first indications of the nonlinear quantum nature of the optomechanical interaction even for singlephoton coupling strengths significantly smaller than the cavity linewidth.
Ultrafast nonlinear dynamics of surface plasmon polaritons in gold
nanowires due to the intrinsic nonlinearity of metals
A. Marini, M. Conforti, G. Della Valle, H. W. Lee, Tr X. Tran, W. Chang, M. A. Schmidt, S. Longhi, P. St J. Russell, F. Biancalana, et al.
Starting from first principles, we theoretically model the nonlinear temporal dynamics of goldbased plasmonic devices resulting from the heating of their metallic components. At optical frequencies, the gold susceptibility is determined by the interband transitions around the X, L points in the first Brillouin zone, and thermomodulational effects ensue from Fermi smearing of the electronic energy distribution in the conduction band. As a consequence of lightinduced heating of the conduction electrons, the optical susceptibility becomes nonlinear. In this paper we describe, for the first time to our knowledge, the effects of the thermomodulational nonlinearity of gold on the propagation of surface plasmon polaritons guided on gold nanowires. We introduce a novel nonlinear Schrodingerlike equation to describe pulse propagation in such nanowires, and we predict the appearance of an intense spectral redshift caused by the delayed thermal response.
Experimental Observation of Discrete Solitons in a Temporal Photonic
Lattice
Martin Wimmer, Alois Regensburger, Christoph Bersch, MohammadAli Miri, Georgy Onishchukov, Demetrios N. Christodoulides, Ulf Peschel
Conference on Lasers and ElectroOptics
(2013)
We report the first experimental observation of solitons propagating in discrete steps through a temporal photonic lattice, which is implemented in a fiberloop setup. Stable propagation over fifty coupling lengths is achieved.
Measuring mechanical strain and twist using helical photonic crystal
fiber
Xiaoming Xi, Gordon K. L. Wong, Thomas Weiss, Philip St J. Russell
Solidcore photonic crystal fiber (PCF) with a permanent helical twist exhibits dips in its transmission spectrum at certain wavelengths. These are associated with the formation of orbital angular momentum states in the cladding. Here we investigate the tuning of these states with mechanical torque and axial tension. The dip wavelengths are found to scale linearly with both axial strain and mechanical twist rate. Analysis shows that the tensioninduced shift in resonance wavelength is determined both by the photoelastic effect and by the change in twist rate, while the torsioninduced wavelength shift depends only on the change in twist rate. Twisted PCF can act as an effective optically monitored torquetension transducer, twist sensor, or strain gauge. (C) 2013 Optical Society of America
Quantum versus classical polarization states: when multipoles count
L. L. SanchezSoto, A. B. Klimov, P. de la Hoz, G. Leuchs
JOURNAL OF PHYSICS BATOMIC MOLECULAR AND OPTICAL PHYSICS
46(10)
104011
(2013)

Journal
We advocate a simple multipole expansion of the polarization density matrix. The resulting multipoles are used to construct bona fide quasiprobability distributions that appear as a sum of successive moments of the Stokes variables, the first one corresponding to the classical picture on the Poincare sphere. We employ the particular case of the Q function to formulate a whole hierarchy of measures that properly assess higherorder polarization correlations.
Ultrafast coherent nanoscopy
XueWen Chen, Ahmad Mohammadi, Amir Hossein Baradaran Ghasemi, Mario Agio
The dramatic advances of nanotechnology experienced in recent years enabled us to fabricate optical nanostructures or nanoantennas that greatly enhance the conversion of localised electromagnetic energy into radiation and vice versa. Nanoantennas offer the required improvements in terms of bandwidth, interaction strength and resolution for combining ultrafast spectroscopy, nanooptics and quantum optics to fundamentally push forward the possibility of the coherent optical access on individual nanostructures or even molecules above cryogenic temperatures, where dephasing processes typically occur at very short time scales. In this context, we discuss recent progress in the theoretical description of lightmatter interaction at the nanoscale and related experimental findings. Moreover, we present concrete examples in support of our vision and propose a series of experiments that aim at exploring novel promising regimes of optical coherence and quantum optics in advanced spectroscopy. We envisage extensions to ultrafast and nonlinear phenomena, especially in the direction of multidimensional nanoscopy.
Observation of acoustically induced modulation instability in a
Brillouin photonic crystal fiber laser
We report the experimental observation of selfinduced modulation instability (MI) in a Brillouin fiber laser made with a solidcore photonic crystal fiber (PCF) with strong anomalous dispersion. We identify this MI as the result of parametric amplification of optical sidebands generated by guided acoustic modes within the core of the PCF. It is further shown that MI leads to passive harmonic mode locking and to the generation of a picosecond pulse train at a repetition rate of 1.15 GHz which matches the acoustic frequency of the fundamental acoustic mode of the PCF. (C) 2013 Optical Society of America
Observation of Defect States in PTSymmetric Optical Lattices
Alois Regensburger, MohammadAli Miri, Christoph Bersch, Jakob Naeger, Georgy Onishchukov, Demetrios N. Christodoulides, Ulf Peschel
We provide the first experimental demonstration of defect states in paritytime (PT) symmetric meshperiodic potentials. Our results indicate that these localized modes can undergo an abrupt phase transition in spite of the fact that they remain localized in a PTsymmetric periodic environment. Even more intriguing is the possibility of observing a linearly growing radiation emission from such defects provided their eigenvalue is associated with an exceptional point that resides within the continuum part of the spectrum. Localized complex modes existing outside the bandgap regions are also reported along with their evolution dynamics.
A Simplified Implementation of the Bubble Analysis of Biopolymer Network
Pores
Selfassembled GaN rods were grown on sapphire by metalorganic vapor phase epitaxy using a simple twostep method that relies first on a nitridation step followed by GaN epitaxy. The maskfree rods formed without any additional catalyst. Most of the vertically aligned rods exhibit a regular hexagonal shape with sharp edges and smooth sidewall facets. Cathodoand microphotoluminescence investigations were carried out on single GaN rods. Whispering gallery modes with quality factors greater than 4000 were measured demonstrating the high morphological and optical quality of the selfassembled GaN rods. (C) 2012 Optical Society of America
Subwavelength solitons and Faraday waves in twodimensional lattices of
metal nanoparticles
Roman E. Noskov, Daria A. Smirnova, Yuri S. Kivshar
We demonstrate that optically driven twodimensional lattices of nonlinear metal nanoparticles can support a variety of dissipative localized modes including Faraday ripples, trapped and walking solitons, oscillons, and switching waves connecting different polarization states. (C) 2013 Optical Society of America
Structure and mechanics of fibrin clots formed under mechanical
perturbation
S. Muenster, L. M. Jawerth, B. Fabry, D. A. Weitz
JOURNAL OF THROMBOSIS AND HAEMOSTASIS
11(3)
557560
(2013)

Journal
Parametric resonance in periodically tapered optical fibres: scalar and
vectorial modulational instability bands
A. Armaroli, F. Biancalana
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Interferometric homogeneity test using adaptive frequency comb
illumination
The homogeneity test of glass plates in a Fizeau interferometer requires the measurement of the glass sample in reflected as well as in transmitted light. For the measurement in transmitted light, the sample has to be inserted into the ray path of a Fizeau or TwymanGreen interferometer, which leads to a nested cavity setup. To separate the interference signals from the different cavities, we illuminate a Fizeau interferometer with an adaptive frequency comb. In this way, rigid glass plates can be measured, and linear variations in the homogeneity can also be detected. The adaptive frequency comb is provided by a variable FabryPerot filter under broadband illumination from a superluminescence diode. Compared to approaches using a twobeam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher. (C) 2013 Optical Society of America
Total internal reflection of orbital angular momentum beams
W. Loffler, N. Hermosa, Andrea Aiello, J. P. Woerdman
We investigate how beams with orbital angular momentum (OAM) behave under total internal reflection. This is studied in two complementary experiments: in the first experiment, we study geometric shifts of OAM beams upon total internal reflection (GoosHanchen and ImbertFedorov shifts, for each the spatial and angular variant), and in the second experiment we determine changes in the OAM mode spectrum of a beam, again upon total internal reflection. As a result we find that, in the first case, the shifts are independent of OAM and beam focusing, while in the second case, modifications in the OAM spectrum occur which depend on the input OAM mode as well as on the beam focusing. This is investigated by experiment and theory. We also show how the two methods, beam shifts on the one hand, and OAM spectrum changes on the other, are related theoretically.
The photonic wheel  demonstration of a state of light with purely
transverse angular momentum
P. Banzer, M. Neugebauer, A. Aiello, C. Marquardt, N. Lindlein, T. Bauer, G. Leuchs
JOURNAL OF THE EUROPEAN OPTICAL SOCIETYRAPID PUBLICATIONS
8
13032
(2013)

Journal
In classical mechanics, a system may possess angular momentum which can be either transverse (e.g. in a spinning wheel) or longitudinal (e.g. for a spiraling seed falling from a tree) with respect to the direction of motion. However, for light, a typical massless wave system, the situation is less versatile. Photons are wellknown to exhibit intrinsic angular momentum which is longitudinal only: the spin angular momentum defining the polarization and the orbital angular momentum associated with a spiraling phase front. Here we show that it is possible to generate a novel state of the light field that contains purely transverse angular momentum, the analogue of a spinning mechanical wheel. We realize this state by tight focusing of a polarization tailored light beam and measure it using an optical nanoprobing technique. Such a novel state of the light field can find applications in optical tweezers and spanners where it allows for additional rotational degree of freedom not achievable in singlebeam configurations so far.
Photoionizationinduced Nonlinear Phenomena in Gasfilled Photonic
Crystal Fibers
Mohammed F. Saleh, Fabio Biancalana
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
We study the interband selfinduced transmission of surface plasmon polaritons in a gold film surrounded by an external Kerr medium. We model the optical propagation by using a version of the generalized nonlinear Schrodinger equation for the field envelope coupled to Bloch equations for valence electrons of gold, predicting selfinduced transparency of ultrashort plasmon solitons with a pulse duration below 10 fs. We demonstrate that the Kerr nonlinearity from the surrounding dielectric can be used to compensate for the group velocity dispersion, and that the impact of dephasing and decay processes can be effectively reduced by the selfinduced transmission mechanism.
Nonlinear intermodal interactions in gasfilled hollowcore photonic
crystal fibre
Francesco Tani, John C. Travers, Philip St. J. Russell
Conference on Lasers and ElectroOptics
(2013)
The emission of pressuretunable ultraviolet dispersive waves into higherorder modes of a gasfilled kagomePCF is experimentally and numerically demonstrated. Numerical evidence of a balance between Kerrdriven selffocusing and plasmadefocusing is also presented.
Efficient AntiStokes Generation via Stimulated Raman Scattering in a
H2filled HollowCore PCF
B. M. Trabold, A. Abdolvand, A. M. Walser, P. St. J. Russell
Conference on Lasers and ElectroOptics
(2013)
Forward stimulated Raman scattering is used to generate a strong antiStokes signal in a hydrogenfilled hollowcore photonic crystal fibre (PCF). Phasematching is achieved using higherorder modes and is controlled with a spatial light modulator.
8Q AM regeneration using a phasesensitive amplifier with
dualconjugated pumps
B. Stiller, G. Onishchukov, B. Schmauss, G. Leuchs
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Macroscopic HongOuMandel interference
T. Sh Iskhakov, K. Yu Spasibko, M. V. Chekhova, G. Leuchs
We report on a HongOuMandel interference experiment for twin beams with photon numbers per mode as large as 10(6) generated via highgain parametric down conversion (PDC). The standard technique of coincidence counting leads in this case to a dip with a very low visibility. By measuring, instead of coincidence counting rate, the variance of the photonnumber difference, we observe an extremely wellpronounced peak. From the shape of the peak, one can infer information about the spectral properties of the PDC radiation, including the number of frequency/temporal modes.
Diffractive resonant radiation by spatial solitons in waveguide arrays
Truong X. Tran, Fabio Biancalana
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Two techniques for temporal pulse compression in gasfilled hollowcore
kagome photonic crystal fiber
K. F. Mak, J. C. Travers, N. Y. Joly, A. Abdolvand, P. St. J. Russell
We demonstrate temporal pulse compression in gasfilled kagome hollowcore photonic crystal fiber (PCF) using two different approaches: fibermirror compression based on selfphase modulation under normal dispersion, and soliton effect selfcompression under anomalous dispersion with a decreasing pressure gradient. In the first, efficient compression to neartransformlimited pulses from 103 to 10.6 fs was achieved at output energies of 10.3 mu J. In the second, compression from 24 to 6.8 fs was achieved at output energies of 6.6 mu J, also with neartransformlimited pulse shapes. The results illustrate the potential of kagomePCF for postprocessing the output of fiber lasers. We also show that, using a negative pressure gradient, ultrashort pulses can be delivered directly into vacuum. (C) 2013 Optical Society of America
A. M. Cubillas, M. Schmidt, T. G. Euser, B. J. M. Etzold, N. Taccardi, S. Unterkofler, P. Wasserscheid, P. St. J. Russell
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Strain history dependence of the nonlinear stress response of fibrin and
collagen networks
Stefan Muenster, Louise M. Jawerth, Beverly A. Leslie, Jeffrey I. Weitz, Ben Fabry, David A. Weitz
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF
AMERICA
110(30)
1219712202
(2013)

Journal
We show that the nonlinear mechanical response of networks formed from uncrosslinked fibrin or collagen type I continually changes in response to repeated largestrain loading. We demonstrate that this dynamic evolution of the mechanical response arises from a shift of a characteristic nonlinear stressstrain relationship to higher strains. Therefore, the imposed loading does not weaken the underlying matrices but instead delays the occurrence of the strain stiffening. Using confocal microscopy, we present direct evidence that this behavior results from persistent lengthening of individual fibers caused by an interplay between fiber stretching and fiber buckling when the networks are repeatedly strained. Moreover, we show that covalent crosslinking of fibrin or collagen inhibits the shift of the nonlinear material response, suggesting that the molecular origin of individual fiber lengthening may be slip of monomers within the fibers. Thus, a fibrous architecture in combination with constituents that exhibit internal plasticity creates a material whose mechanical response adapts to external loading conditions. This design principle may be useful to engineer novel materials with this capability.
Increasing the Dimensionality of Quantum Walks Using Multiple Walkers
Peter P. Rohde, Andreas Schreiber, Martin Stefanak, Igor Jex, Alexei Gilchrist, Christine Silberhorn
JOURNAL OF COMPUTATIONAL AND THEORETICAL NANOSCIENCE
10(7)
16441652
(2013)

Journal
We show that with the addition of multiple walkers, quantum walks on a line can be transformed into lattice graphs of higher dimension. Thus, multiwalker walks can simulate singlewalker walks on higher dimensional graphs and vice versa. This exponential complexity opens up new applications for presentday quantum walk experiments. We discuss the applications of such higherdimensional structures and how they relate to linear optics quantum computing. In particular we show that multiwalker quantum walks are equivalent to the BOSONSAMPLING model for linear optics quantum computation proposed by Aaronson and Arkhipov. With the addition of control over phasedefects in the lattice, which can be simulated with entangling gates, asymmetric lattice structures can be constructed which are universal for quantum computation.
Extraction of plasticity parameters of GaN with high temperature, in
situ microcompression
J. M. Wheeler, C. Niederberger, C. Tessarek, S. Christiansen, J. Michler
INTERNATIONAL JOURNAL OF PLASTICITY
40
140151
(2013)

Journal
Micropillar compression has been utilised in a novel elevated temperature technique, in situ in the SEM to characterise the plasticity of gallium nitride (GaN) {0001}oriented euhedral prisms grown by metallorganic vapor phase epitaxy. Electron backscatter diffraction was used to confirm the orientation of the prisms, and deformation was observed to occur via 2nd order pyramidal slip on the (11 (2) over bar2)(11 (2) over bar3) slip system. Analysis of the microcompression data allowed extraction of fundamental deformation parameters of GaN from 24.5 to 479.3 degrees C. The strain rate sensitivity parameter was determined to be 0.0234 +/ 0.0073 both by constant strain rate microcompressions and microcompression strain rate jump tests. The measured activation volume was 3.88 +/ 0.13 x 10(29) m(3), and the activation energy was 0.9 +/ 0.2 eV. (c) 2012 Elsevier Ltd. All rights reserved.
Amplification of realistic Schrodingercatstatelike states by homodyne
heralding
Amine Laghaout, Jonas S. NeergaardNielsen, Ioannes Rigas, Christian Kragh, Anders Tipsmark, Ulrik L. Andersen
We present a scheme for the amplification of Schrodinger cat states that collapses two smaller states onto their constructive interference via a homodyne projection. We analyze the performance of the amplification in terms of fidelity and success rate when the input consists of either exact coherent state superpositions or of photonsubtracted squeezed vacua. The impact of imprecise homodyne detection and of impure squeezing is quantified. We also assess the scalability of iterated amplifications. DOI: 10.1103/PhysRevA.87.043826
Geometrical optimization and contact configuration in radial pn junction
silicon nanorod and microrod solar cells
F. Voigt, T. Stelzner, S. Christiansen
PROGRESS IN PHOTOVOLTAICS
21(8)
15671579
(2013)

Journal
Electric charge transport simulations of symmetrically doped radial pn junction silicon nanorod solar cells were performed using the Technology Computeraided Design software suite by Silvaco. Two schemes of electric contacting were applied, the first one consisting of a cathode wrapped around the cladding of the rod and the second one in a cathode located only on the top rod surface. In both cases, the anode was implemented just below the bottom end of the ptype rod core. Ptype cores and ntype shells of the rods were assumed, with dopant densities of 10(18)cm(3) in both regions. The location of the pn junction was chosen such that wellformed space charge regions could be established with the outer end of the ntype depletion region being adjacent to the cylindric surface of the nanorod. Rod radii and rod lengths were varied and optimized in a threestep process for both types of contacting schemes. It was found that inhomogeneous carrier generation profiles diminish the opencircuit voltage in case of a wrapped cathode configuration. Most realistic is the usage of a top contact configuration with rod radii of 2 mu m and lengths of around 100 mu m, leading to a cell efficiency of about 15%. Further enhancement of performance is expected, if light trapping of the nanorod layer is taken into account and photonic light harvesting is applied. Copyright (c) 2012 John Wiley & Sons, Ltd.
Interference of conically scattered light in surface plasmon resonance
Aaron Webster, Frank Vollmer
OPTICS LETTERS
38(3)
244246
(2013)
Surface plasmon polaritons on thin metal films are a well studied phenomena when excited using prism coupled geometries such as the Kretschmann attenuated total reflection configuration. Here we describe a novel interference pattern in the conically scattered light emanating from such a configuration when illuminated by a focused beam. We observe conditions indicating only selfinterference of scattered surface plasmon polaritions without any contributions from specular reflection. The spatial evolution of this field is described in the context of Fourier optics and has applications in highly sensitive surface plasmon based biosensing. (C) 2013 Optical Society of America
Optical Activity in Twisted SolidCore Photonic Crystal Fibers
X. M. Xi, T. Weiss, G. K. L. Wong, F. Biancalana, S. M. Barnett, M. J. Padgett, P. St. J. Russell
In this Letter we show that, in spectral regions where there are no orbital cladding resonances to cause transmission loss, the core mode of a continuously twisted photonic crystal fiber (PCF) exhibits optical activity, and that the magnitude of the associated circular birefringence increases linearly with twist rate and is highly reproducible. In contrast to previous work on twistinduced circular birefringence, PCF has zero linear birefringence and an onaxis core, making the appearance of circular birefringence rather unexpected. A theoretical model based on symmetry properties and perturbation theory is developed and used to show that both spin and orbital angular momentum play a role in this effect. It turns out that the degenerate leftand rightcircularly polarized modes of the untwisted PCF are not 100% circularly polarized but carry a small amount of orbital angular momentum caused by the interaction between the core mode and the hollow channels. DOI:10.1103/PhysRevLett.110.143903
Measuring threedimensional interaction potentials using optical
interference
Nassir Mojarad, Vahid Sandoghdar, Madhavi Krishnan
We describe the application of threedimensional (3D) scattering interferometric (iSCAT) imaging to the measurement of spatial interaction potentials for nanoobjects in solution. We study electrostatically trapped gold particles in a nanofluidic device and present details on axial particle localization in the presence of a strongly reflecting interface. Our results demonstrate highspeed (similar to kHz) particle tracking with subnanometer localization precision in the axial and average 2.5 nm in the lateral dimension. A comparison of the measured levitation heights of trapped particles with the calculated values for traps of various geometries reveals good agreement. Our work demonstrates that iSCAT imaging delivers labelfree, highspeed and accurate 3D tracking of nanoobjects conducive to probing weak and longrange interaction potentials in solution. (C) 2013 Optical Society of America
Scalar and vector modulational instability induced by parametric
resonance in periodically tapered PCFs
Andrea Armaroli, Maxime Droques, Arnaud Mussot, Alexandre Kudlinski, Fabio Biancalana
Conference on Lasers and ElectroOptics
(2013)
We analyze the modulational instability process induced by periodic variations of the parameters of a PCF along the propagation direction, induced by an analogue of the parametric resonance in mechanics. (C) 2013 Optical Society of America
The quantum transversefield Ising chain in circuit quantum electrodynamics: effects of disorder on the nonequilibrium dynamics
Oliver Viehmann, Jan von Delft, Florian Marquardt
New Journal of Physics
15
035013
(2013)

Journal

PDF
We study several dynamical properties of a recently proposed implementation of the quantum transversefield Ising chain in the framework of circuit quantum electrodynamics (QED). Particular emphasis is placed on the effects of disorder on the nonequilibrium behavior of the system. We show that small amounts of fabricationinduced disorder in the system parameters do not jeopardize the observation of previously predicted phenomena. Based on a numerical extraction of the mean free path of a wave packet in the system, we also provide a simple quantitative estimate for certain disorder effects on the nonequilibrium dynamics of the circuit QED quantum simulator. We discuss the transition from weak to strong disorder, characterized by the onset of Anderson localization of the system's wave functions, and the qualitatively different dynamics it leads to.
A class of nonparaxial accelerating optical waves is introduced. These are beams with a Bessellike profile that are capable of shifting laterally along fairly arbitrary trajectories as the wave propagates in free space. The concept expands on our previous proposal of paraxial accelerating Bessellike beams to include beams with subwavelength lobes and/or large trajectory angles. Such waves are produced when the phase at the input plane is engineered so that the interfering ray cones are made to focus along the prespecified path. When the angle of these cones is fixed, the beams possess a diffractionfree Bessel profile on planes that stay normal to their trajectory, which can be considered as a generalized definition of diffractionless propagation in the nonparaxial regime. The analytical procedure leading to these results is based on a rayoptics interpretation of RayleighSommerfeld diffraction and is presented in detail. The evolution of the proposed waves is demonstrated through a series of numerical examples and a variety of trajectories.
Dynamics in photonic crystal fiber ring cavities
N. Y. Joly, M. J. Schmidberger, W. Chang, P. St. J. Russell
IEEE Photonics Conference
499500
(2013)
We review recent work on the use of photonic crystal fiber in ringcavitiesan Erdoped fiber laser modelocked at the 337th harmonic by a 1.8GHz acoustic core resonance, and a synchronouslypumped ringcavity for supercontinuum generation.
Oxidefree hybrid silicon nanowires: From fundamentals to applied
nanotechnology
Muhammad Y. Bashouti, Kasra Sardashti, Sebastian W. Schmitt, Matthias Pietsch, Juergen Ristein, Hossam Haick, Silke H. Christiansen
PROGRESS IN SURFACE SCIENCE
88(1)
3960
(2013)

Journal
The ability to control physical properties of silicon nanowires (Si NWs) by designing their surface bonds is important for their applicability in devices in the areas of nanoelectronics, nanophotonics, including photovoltaics and sensing. In principle a wealth of different molecules can be attached to the bare Si NW surface atoms to create e.g. SiO, SiC, SiN, etc. to mention just the most prominent ones. SiO bond formation, i.e. oxidation usually takes place automatically as soon as Si NWs are exposed to ambient conditions and this is undesired is since a defective oxide layer (i.e. native silicon dioxide  SiO2) can cause uncontrolled trap states in the band gap of silicon. Surface functionalization of Si NW surfaces with the aim to avoid oxidation can be carried out by permitting e.g. SiC bond formation when alkyl chains are covalently attached to the Si NW surfaces by employing a versatile twostep chlorination/alkylation process that does not affect the original length and diameter of the NWs. Termination of Si NWs with alkyl molecules through covalent SiC bonds can provide long term stability against oxidation of the Si NW surfaces. The alkyl chain length determines the molecular coverage of Si NW surfaces and thus the surface energy and next to simple SiC bonds even bond types such as C=C and C=C can be realized. When integrating differently functionalized Si NWs in functional devices such as field effect transistors (FETs) and solar cells, the physical properties of the resultant devices vary. (C) 2013 Elsevier Ltd. All rights reserved.
Mid infrared supercontinuum generation in nanotapered
chalcogenidesilica stepindex waveguides
N. Granzow, M. A. Schmidt, W. Chang, L. Wang, Q. Coulombier, J. Troles, P. Toupin, I. Hartl, K. F. Lee, M. E. Fermann, et al.
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Decorrelated PDC Source at Telecom Wavelengths with Identical Signal and
Idler
Georg Harder, Vahid Ansari, Benjamin Brecht, Thomas Dirmeier, Christoph Marquardt, Christine Silberhorn
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Simulations of two particle dynamics employing dynamic coin control in
2D quantum walks
Andreas Schreiber, Fabian Katzschmann, Aurel Gabris, Peter P. Rohde, Kaisa Laiho, Martin Stefanak, Craig Hamilton, Igor Jex, Christine Silberhorn
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Experimental Investigation of a Single Chrial NanoStructure Made of a
Composite Material
P. Wozniak, K. Hoeflich, S. Fritsch, S. Christiansen, P. Banzer, G. Leuchs
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Two Schemes for Pulse Compression in GasFilled KagomePCF
Ka Fai Mak, John C. Travers, Nicolas Y. Joly, Amir Abdolvand, Philip St. J. Russell
Conference on Lasers and ElectroOptics
(2013)
Two schemes for multimu J pulse compression in noblegasfilled hollowcore kagomePCF are demonstrated and compared. A fiberpluschirpedmirror combination compresses 150 fs, 9.5 mu J pulses to 26 fs, and solitoneffect compression produces sub 7 fs pulses.
Storage of Light in a HollowCore PhotonicCrystal Fibre
Michael R. Sprague, Patrick Michelberger, Tessa F. M. Champion, Duncan G. England, Joshua Nunn, W. Steven Kolthammer, XianMin Jin, Amir Abdolvand, Philip St. J. Russell, Ian A. Walmsley, et al.
Conference on Lasers and ElectroOptics
(2013)
We report the storage and retrieval of broadband optical pulses using a Raman interaction in a roomtemperature ensemble of cesium atoms confined in a hollowcore photoniccrystal fibre. (C) 2013 Optical Society of America
Frequency upconversion and pulse compression mediated by soliton plasma
interactions in gasfilled photonic crystal fiber
Philipp Hoelzer, Wonkeun Chang, John C. Travers, Philip St J. Russell
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
A gold nanotip enhanced optical fibre device for plasmonic nearfield
microscopy
P. Uebel, S. T. Bauerschmidt, M. A. Schmidt, P. St J. Russell
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Functional Plasmonic Nanocircuits with Low Insertion and Propagation
Losses
Arian Kriesch, Stanley P. Burgos, Daniel Ploss, Hannes Pfeifer, Harry A. Atwater, Ulf Peschel
We experimentally demonstrate plasmonic nanocircuits operating as subdiffraction directional couplers optically excited with high efficiency from freespace using optical YagiUda style antennas at lambda(0) = 1550 nm. The optical YagiUda style antennas are designed to feed channel plasmon waveguides with high efficiency (45% in coupling, 60% total emission), narrow angular directivity (<40 degrees), and low insertion loss. SPP channel waveguides exhibit propagation lengths as large as 34 mu m with adiabatically tuned confinement and are integrated with ultracompact (5 x 10 mu m(2)), highly dispersive directional couplers, which enable 30 dB discrimination over Delta lambda = 200 nm with only 0.3 dB device loss.
NearInfrared Spectroscopy on a Single Photon Level
Michael Foertsch, Thomas Gerrits, Martin J. Stevens, Josef U. Fuerst, Gerhard Schunk, Florian Sedlmeir, Harald G. L. Schwefel, Dmitry Strekalov, Sae Woo Nam, Gerd Leuchs, et al.
2013 CONFERENCE ON LASERS AND ELECTROOPTICS PACIFIC RIM (CLEOPR)
(2013)
We present a spectroscopy technique on the single photon level by combining a widely wavelength tunable single photon source based on a crystalline whispering gallery mode resonator with an energy resolving transition edge sensor.
Observation of modulationally unstable multiwave mixing
J. Fatome, C. Finot, A. Armaroli, S. Trillo
OPTICS LETTERS
38(2)
181183
(2013)
We demonstrate experimentally that multiple fourwave mixing (FWM) pumped by a dualfrequency input in a singlemode fiber is modulationally unstable. This collective type of instability leads, in the anomalous dispersion regime, to sideband growth around all orders of FWM. This is in contrast with the normal dispersion regime where our measurements show that FWM exhibits no instability. Our conclusions are based on the first systematic mapping of the phenomenon as a function of the dualpump input frequency separation. (C) 2013 Optical Society of America
Multiphoton nonclassical correlations in entangled squeezed vacuum
states
Bhaskar Kanseri, Timur Iskhakov, Georgy Rytikov, Maria Chekhova, Gerd Leuchs
Photonnumber correlation measurements are performed on bright squeezed vacuum states using a standard Belltest setup, and quantum correlations are observed for conjugate polarizationfrequency modes. We further test the entanglement witnesses for these states and demonstrate the violation of the separability criteria, which infers that all of the macroscopic Bell states, containing typically 10(6) photons per pulse, are polarization entangled. The study also reveals the symmetry of macroscopic Bell states with respect to local polarization transformations. DOI: 10.1103/PhysRevA.87.032110
Identical classical particles: Half fermions and half bosons
We study the problem of particle indistinguishability for the three cases known in nature: identical classical particles, identical bosons, and identical fermions. By exploiting the fact that different types of particles are associated with Hilbert space vectors with different symmetries, we establish some relations between the expectation value of several different operators, as the particle number one and the interparticle correlation one, evaluated for states of a pair of identical classical particles, bosons, and fermions. We find that the quantum behavior of a pair of identical classical particles has exactly half fermionic and half bosonic characteristics.
Impulsive Ramaninduced spectral broadening in hydrogenfilled HCPCF
F. Belli, A. Abdolvand, J. C. Travers, W. Chang, A. M. Walser, P. St J. Russell
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
OneStep Synthesis of PEGCoated Gold Nanoparticles by Rapid Microwave
Heating
Seung Kwon Seol, Daeho Kim, Sunshin Jung, Won Suk Chang, Ji Tae Kim
Polyethylene Glycol(PEG) coated gold nanoparticles (PEGAuNPs) are synthesized by a onestep route with rapid microwave heating. Homogeneous nucleation of the primary gold particles is enhanced by increasing the applied microwave power during the initial stage of the synthesis, increasing the temperature ramping rate (Rr) and resulting in decreased size and improved uniformity of the synthesized PEGAuNPs. Using rapid microwave heating, we successfully produce uniform colloidal PEGAuNPs with an average diameter of 14.3 +/ 2.5 nm within a few minutes. By appropriate tuning of the growth parameters, microwave synthesis can produce largely colloidal PEGAuNPs with high uniformity.
Entanglement of macroscopic Bell states
T. Iskhakov, B. Kanseri, G. Rytikov, M. Chekhova, G. Leuchs
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Bound states in a temporal fiber network with paritytime symmetry
Alois Regensburger, MohammadAli Miri, Christoph Bersch, Jakob Naeger, Georgy Onishchukov, Demetrios N. Christodoulides, Ulf Peschel
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Combined soliton pulse compression and plasmarelated frequency
upconversion in gasfilled photonic crystal fiber
W. Chang, P. Hoelzer, J. C. Travers, P. St. J. Russell
We numerically investigate selffrequency blueshifting of a fundamental soliton in a gasfilled hollowcore photonic crystal fiber. Because of the changing underlying soliton parameters, the blueshift gives rise to adiabatic soliton compression. Based on these features, we propose a device that enables frequency shifting over an octave and pulse compression from 30 fs down to 2.3 fs. (C) 2013 Optical Society of America
Solitonradiation trapping in gasfilled photonic crystal fibers
We propose an optical trapping technique in which a fundamental soliton traps an ultrashort small amplitude radiation in a symmetric hollowcore photonic crystal fiber filled with a noble gas, preventing its dispersion. The system is Raman and plasmafree. Trapping is due to the cross phase modulation effect between the two pulses. The trapped radiation inside the solitoninduced potential will oscillate periodically due to the shock effect, similar to the motion of a mechanical pendulum. DOI: 10.1103/PhysRevA.87.043807
Fourthorder dispersion mediated modulation instability in dispersion
oscillating fibers
Maxime Droques, Alexandre Kudlinski, Geraud Bouwmans, Gilbert Martinelli, Arnaud Mussot, Andrea Armaroli, Fabio Biancalana
We investigate the role played by fourthorder dispersion on the modulation instability process in dispersion oscillating fibers. It not only leads to the appearance of instability sidebands in the normal dispersion regime (as in uniform fibers), but also to a new class of large detuned instability peaks that we ascribe to the variation of dispersion. All these theoretical predictions are experimentally confirmed. (C) 2013 Optical Society of America
Tunable vacuumUV to visible ultrafast pulse source based on gasfilled
KagomePCF
Ka Fai Mak, John C. Travers, Philipp Hoelzer, Nicolas Y. Joly, Philip St. J. Russell
An efficient and tunable 176550 nm source based on the emission of resonant dispersive radiation from ultrafast solitons at 800 nm is demonstrated in a gasfilled hollowcore photonic crystal fiber (PCF). By careful optimization and appropriate choice of gas, informed by detailed numerical simulations, we show that bright, high quality, localized bands of UV light (relative widths of a few percent) can be generated at all wavelengths across this range. Pulse energies of more than 75 nJ in the deepUV, with relative bandwidths of similar to 3%, are generated from pump pulses of a few mu J. Excellent agreement is obtained between numerical and experimental results. The effects of positive and negative axial pressure gradients are also experimentally studied, and the coherence of the deepUV dispersive wave radiation numerically investigated. (C) 2013 Optical Society of America
Nonlinear crossKerr quasiclassical dynamics
I. Rigas, A. B. Klimov, L. L. SanchezSoto, G. Leuchs
We study the quasiclassical dynamics of the crossKerr effect. In this approximation, the typical periodical revivals of the decorrelation between the two polarization modes disappear and remain entangled. By mapping the dynamics onto the Poincare space, we find simple conditions for polarization squeezing. When dissipation is taken into account, the shape of the states in such a space is not considerably modified, but their size is reduced.
The Role of Hole Transport in Hybrid Inorganic/Organic
Silicon/Poly(3,4ethylenedioxythiophene):Poly(styrenesulfonate)
Heterojunction Solar Cells
Matthias Pietsch, Muhammad Y. Bashouti, Silke Christiansen
JOURNAL OF PHYSICAL CHEMISTRY C
117(18)
90499055
(2013)

Journal
In this paper, the fundamental advantage of highly conductive transparent polymers as hole transport layers in hybrid solar cells is demonstrated. The substantial efficiency improvement of hybrid ntype silicon (nSi)/poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cells by adding organic solvents to the polymer dispersion is investigated, and a model that explains reasons and mechanisms for that improvement is given. Opencircuit voltages of 600 mV were measured, which are comparable to conventional diffused silicon pnjunction wafer cells. It is shown by means of Xray photoelectron spectroscopy that the PEDOT versus PSS ratio plays an important role for charge carrier transport in the PEDOT:PSS layer as well as for charge carrier separation at the nSi/PEDOT:PSS interface. A shell of insulating PSS segregates at the surface of PEDOT:PSS grains and represents a considerable barrier for charge carrier transport and charge carrier separation, influencing the conductivity of the polymer film and the opencircuit voltage of a processed solar cell, respectively. It could be demonstrated that a mixing of the PEDOT:PSS polymer blend with the organic solvent dimethylsulfoxide reduces the PSS insulator segregation at the surface of PEDOT:PSS grains and improves the performance of hybrid nSi/PEDOT:PSS solar cells.
PHzwide Supercontinua of Nondispersing Subcycle Pulses Generated by
Extreme Modulational Instability
Modulational instability (MI) of 500 fs, 5 mu J pulses, propagating in gasfilled hollowcore kagome photonic crystal fiber, is studied numerically and experimentally. By tuning the pressure and launched energy, we control the duration of the pulses emerging as a consequence of MI and hence are able to study two regimes: the classical MI case leading to fewcycle solitons of the nonlinear Schrodinger equation; and an extreme case leading to the formation of nondispersing subcycle pulses (0.5 to 2 fs) with peak intensities of order 10(14) Wcm(2). Insight into the two regimes is obtained using a novel statistical analysis of the soliton parameters. Numerical simulations and experimental measurements show that, when a train of these pulses is generated, strong ionization of the gas occurs. This extreme MI is used to experimentally generate a high energy (> 1 mu J) and spectrally broad supercontinuum extending from the deep ultraviolet (320 nm) to the infrared (1300 nm).
Selffrequency blueshift of dissipative solitons in siliconbased
waveguides
We analyze the dynamics of dissipative solitons in silicon on insulatorwaveguides embedded in a gain medium. The optical propagation is modeled through a cubicGinzburgLandau equation for the field envelope coupled with an ordinary differential equation accounting for the generation of free carriers owing to twophoton absorption. Our numerical simulations clearly indicate that dissipative solitons accelerate due to the carrierinduced index change and experience a considerable blueshift, which is mainly hampered by the gain dispersion of the active material. Numerical results are fully explained by analytical predictions based on soliton perturbation theory.
Lightmatter interaction in free space
Gerd Leuchs, Markus Sondermann
JOURNAL OF MODERN OPTICS
60(1)
3642
(2013)

Journal
We review recent experimental advances in the field of efficient coupling of single atoms and light in free space. Furthermore, a comparison of efficient free space coupling and strong coupling in cavity quantum electrodynamics (QED) is given. Free space coupling does not allow for observing oscillatory exchange between the light field and the atom which is the characteristic feature of strong coupling in cavity QED. Like cavity QED, free space QED does, however, offer full switching of the light field, a 180 degrees phase shift conditional on the presence of a single atom as well as 100% absorption probability of a single photon by a single atom. Furthermore, free space cavity QED comprises the interaction with a continuum of modes.
Polarization assisted fast data encoding and transmission using
coherence based spectral anomalies
Two methods for fast information encoding and free space communication are proposed, which are based on the rapid transitions in coherencebased (spatial and temporal) spectral anomalies called 'spectral switches'. The information (data bits) could be encoded in terms of red and blue shifts in the source spectrum. The encoding process itself could be made fast by polarization assisted switching of spectral anomalies using a polarization selective device such as an electrooptic modulator. The advantages and limitations of this polarization based data processing mechanism are also discussed.
Highenergy, shockfrontassisted resonant radiation in the normal
dispersion regime
Thomas Roger, Mohammed F. Saleh, Samudra Roy, Fabio Biancalana, Chunyong Li, Daniele Faccio
We present a simple yet effective theory that predicts the existence of resonant radiation bands in the deep normal groupvelocity dispersion region of a medium, even in the absence of a zerogroupvelocity dispersion point. This radiation is evident when the medium is pumped with highenergy ultrashort pulses, and it is driven by the interplay between the Kerr and the shock terms in the nonlinear Schrodinger equation. Accurate experiments performed in bulk silica fully support the theoretical phasematching condition found by our theory.
Classical optics representation of the quantum mechanical translation
operator via ABCD matrices
The ABCD matrix formalism describing paraxial propagation of optical beams across linear systems is generalized to arbitrary beam trajectories. As a byproduct of this study, a onetoone correspondence between the extended ABCD matrix formalism presented here and the quantum mechanical translation operator is established.
Beating the OneHalf Limit of AncillaFree Linear Optics Bell
Measurements
We show that optically encoded twoqubit Bell states can be unambiguously discriminated with a success probability of more than 50% in both singlerail and dualrail encodings by using active linearoptical resources that include Gaussian squeezing operations. These results are in contrast to the wellknown upper bound of 50% for unambiguous discrimination of dualrail Bell states using passive, static linear optics and arbitrarily many vacuum modes. We present experimentally feasible schemes that improve the success probability to 64.3% in dualrail and to 62.5% in singlerail for a uniform random distribution of Bell states. Conceptually, this demonstrates that neither interactions that induce nonlinear mode transformations (such as Kerr interactions) nor auxiliary entangled photons are required to go beyond the onehalf limit. We discuss the optimality of our singlerail scheme and talk about an application of our dualrail scheme in quantum communication.
Enhancing Whispering Gallery Mode Biosensing
Frank Vollmer
International Conference on Transparent Optical NetworksICTON
(2013)
First, years of work on advancing the device physics and engineering of WGM biosensors has improved the ultimate physical detection limits of WGM transducers, yet the limits for DNA detection by hybridization has plateaued. Molecular recognition of DNA at a surface limits the biosensors' sensitivity, specificity, and reusability. It is therefore imperative to integrate novel molecular approaches with existing labelfree transducers to overcome those limitations. I will demonstrate this concept by integrating a DNA strand displacement circuit with a whispering gallery mode (WGM) biosensor. Second, by perfecting the fabrication of a glass microsphere WGM resonators by melting optical fibers, we are able to achieve Q factors close to this physical theoretical limit in solution, resulting in, for example, a detection limit of single InfluenzaA virus particles with a molecular weight MW similar to 300,000 kD. This is impressive, but falls several orders of magnitude short of being able to, for example, detect individual biomolecules. I will speak about the theoretical and experimental approaches for further enhancing the already extreme sensitivity of optical resonators with the principle of plasmon resonance, creating regions of high field intensity with subwavelength plasmonic nanoparticles and setting up hybrid photonicplasmonic modes.
The phase shift induced by a single atom in free space
M. Sondermann, G. Leuchs
JOURNAL OF THE EUROPEAN OPTICAL SOCIETYRAPID PUBLICATIONS
8
13052
(2013)

Journal
In this article we theoretically study the phase shift a single atom imprints onto a coherent state light beam in free space. The calculations are performed in a semiclassical framework. The key parameters governing the interaction and thus the measurable phase shift are the solid angle from which the light is focused onto the atom and the overlap of the incident radiation with the atomic dipole radiation pattern. The analysis includes saturation effects and discusses the associated Kerrtype nonlinearity of a single atom.
Ramanfree nonlinear optical effects in high pressure gasfilled hollow
core PCF
M. Azhar, G. K. L. Wong, W. Chang, N. Y. Joly, P. St J. Russell
The effective Kerr nonlinearity of hollowcore kagomestyle photonic crystal fiber (PCF) filled with argon gas increases to similar to 15% of that of bulk silica glass when the pressure is increased from 1 to 150 bar, while the zero dispersion wavelength shifts from 300 to 900 nm. The group velocity dispersion of the system is uniquely pressuretunable over a wide range while avoiding Raman scatteringabsent in noble gasesand having an extremely high optical damage threshold. As a result, detailed and wellcontrolled studies of nonlinear effects can be performed, in both normal and anomalous dispersion regimes, using only a fixedfrequency pump laser. For example, the absence of Raman scattering permits clean observation, at high powers, of the interaction between a modulational instability sideband and a solitoncreated dispersive wave. Excellent agreement is obtained between numerical simulations and experimental results. The system has great potential for the realization of reconfigurable supercontinuum sources, wavelength convertors and shortpulse laser systems. (C)2013 Optical Society of America
ContinuousWave SubTHz Photonic Generation With UltraNarrow Linewidth,
UltraHigh Resolution, Full Frequency Range Coverage and High LongTerm
Frequency Stability
A. R. Criado, C. de Dios, E. Prior, G. H. Doehler, S. Preu, S. Malzer, H. Lu, A. C. Gossard, P. Acedo
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
3(4)
461471
(2013)

Journal
We report on a photonic system for generation of high quality continuouswave (CW) subTHz signals. The system consists on a gainswitchingbased optical frequency comb generator (GSOFCG), a twoopticalmodes selection mechanism and a nipnip superlattice photomixer. As mode selection mechanism, both selective tunable optical filtering using FabryPerot tunable filters (FPTFs) and Optical Injection Locking (OIL) are evaluated. The performance of the reported system surpasses in orders of magnitude the performance of any commercially available optical mmwave and subTHz generation system in a great number of parameters. It matches and even overcomes those of the best commercially available electronic THz generation systems. The performance parameters featured by our system are: linewidth 10 Hz at 120 GHz, complete frequency range coverage (60140 GHz) with a resolution in the order of 0.1 Hz at 120 GHz (10 of generated frequency), high long term frequency stability (5 Hz deviation over one hour). Most of these values are limited by the measurement instrumentation accuracy and resolution, thus the actual values of the system could be better than the reported ones. The frequency can be extended straightforwardly up to 1 THz extending the OFCG frequency span. This system is compact, robust, reliable, offers a very high performance, especially suited for subTHz photonic local oscillators and high resolution spectroscopy.
Arbitrarily large steadystate bosonic squeezing via dissipation
Andreas Kronwald, Florian Marquardt, Aashish A. Clerk
Physical Review A
88(6)
063833
(2013)

Journal

PDF
We discuss how large amounts of steadystate quantum squeezing (beyond 3 dB) of a mechanical resonator can be obtained by driving an optomechanical cavity with two control lasers with differing amplitudes. The scheme does not rely on any explicit measurement or feedback, nor does it simply involve a modulation of an optical spring constant. Instead, it uses a dissipative mechanism with the driven cavity acting as an engineered reservoir. It can equivalently be viewed as a coherent feedback process, obtained by minimally perturbing the quantum nondemolition measurement of a single mechanical quadrature. This shows that in general the concepts of coherent feedback schemes and reservoir engineering are closely related. We analyze how to optimize the scheme, how the squeezing scales with system parameters, and how it may be directly detected from the cavity output. Our scheme is extremely general, and could also be implemented with, e.g., superconducting circuits.
Full photon statistics of a light beam transmitted through an
optomechanical system
Andreas Kronwald, Max Ludwig, Florian Marquardt
Physical Review A
87(1)
013847
(2013)

Journal

PDF
In this paper, we study the full statistics of photons transmitted through an optical cavity coupled to nanomechanical motion. We analyze the entire temporal evolution of the photon correlations, the Fano factor, and the effects of strong laser driving, all of which show pronounced features connected to the mechanical backaction. In the regime of singlephoton strong coupling, this allows us to predict a transition from subPoissonian to superPoissonian statistics for larger observation time intervals. Furthermore, we predict cascades of transmitted photons triggered by multiphoton transitions. In this regime, we observe Fano factors that are drastically enhanced due to the mechanical motion. DOI: 10.1103/PhysRevA.87.013847
Dynamics of levitated nanospheres: towards the strong coupling regime
T. S. Monteiro, J. Millen, G. A. T. Pender, Florian Marquardt, D. Chang, P. F. Barker
New Journal of Physics
15
015001
(2013)

Journal

PDF
The use of levitated nanospheres represents a new paradigm for the optomechanical cooling of a small mechanical oscillator, with the prospect of realizing quantum oscillators with unprecedentedly high quality factors. We investigate the dynamics of this system, especially in the socalled selftrapping regime, where one or more optical fields simultaneously trap and cool the mechanical oscillator. The determining characteristic of this regime is that both the mechanical frequency omega(M) and singlephoton optomechanical coupling strength parameters g are a function of the optical field intensities, in contrast to usual setups where omega(M) and g are constant for the given system. We also measure the characteristic transverse and axial trapping frequencies of different sized silica nanospheres in a simple optical standing wave potential, for spheres of radii r = 20500 nm, illustrating a protocol for loading single nanospheres into a standing wave optical trap that would be formed by an optical cavity. We use these data to confirm the dependence of the effective optomechanical coupling strength on sphere radius for levitated nanospheres in an optical cavity and discuss the prospects for reaching regimes of strong lightmatter coupling. Theoretical semiclassical and quantum displacement noise spectra show that for larger nanospheres with r greater than or similar to 100 nm a range of interesting and novel dynamical regimes can be accessed. These include simultaneous hybridization of the two optical modes with the mechanical modes and parameter regimes where the system is bistable. We show that here, in contrast to typical singleoptical mode optomechanical systems, bistabilities are independent of intracavity intensity and can occur for very weak laser driving amplitudes.
Photonic Cavity Synchronization of Nanomechanical Oscillators
Physical Review Letters
111(21)
213902
(2013)

Journal

PDF
Synchronization in oscillatory systems is a frequent natural phenomenon and is becoming an important concept in modern physics. Nanomechanical resonators are ideal systems for studying synchronization due to their controllable oscillation properties and engineerable nonlinearities. Here we demonstrate synchronization of two nanomechanical oscillators via a photonic resonator, enabling optomechanical synchronization between mechanically isolated nanomechanical resonators. Optical backaction gives rise to both reactive and dissipative coupling of the mechanical resonators, leading to coherent oscillation and mutual locking of resonators with dynamics beyond the widely accepted phase oscillator (Kuramoto) model. In addition to the phase difference between the oscillators, also their amplitudes are coupled, resulting in the emergence of sidebands around the synchronized carrier signal.
Microparticle manipulation using modal superpositions in airfilled hollowcore photonic crystal fiber
Oliver A. Schmidt, Xin Jiang, Fehim Babic, Tijmen G. Euser, Philip St J. Russell
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Sizing up entanglement in mutually unbiased bases with Fisher
information
J. Rehacek, Z. Hradil, A. B. Klimov, G. Leuchs, L. L. SanchezSoto
An efficient method for assessing the quality of quantum state tomography is developed. Special attention is paid to the tomography of multipartite systems in terms of unbiased measurements. Although the overall reconstruction errors of different sets of mutually unbiased bases are the same, differences appear when particular aspects of the measured system are contemplated. This point is illustrated by estimating the fidelities of genuinely tripartite entangled states.
Optimal working points for continuousvariable quantum channels
Imran Khan, Christoffer Wittmann, Nitin Jain, Nathan Killoran, Norbert Luetkenhaus, Christoph Marquardt, Gerd Leuchs
The most important ability of a quantum channel is to preserve the quantum properties of transmitted quantum states. We experimentally demonstrate a continuousvariable 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.
Local Softening of Information Geometric Indicators of Chaos in
Statistical Modeling in the Presence of QuantumLike Considerations
In a previous paper (C. Cafaro et al., 2012), we compared an uncorrelated 3 D Gaussian statistical model to an uncorrelated 2 D Gaussian statistical model obtained from the former model by introducing a constraint that resembles the quantum mechanical canonical minimum uncertainty relation. Analysis was completed by way of the information geometry and the entropic dynamics of each system. This analysis revealed that the chaoticity of the 2 D Gaussian statistical model, quantified by means of the Information Geometric Entropy (IGE), is softened or weakened with respect to the chaoticity of the 3 D Gaussian statistical model, due to the accessibility of more information. In this companion work, we further constrain the system in the context of a correlation constraint among the system's microvariables and show that the chaoticity is further weakened, but only locally. Finally, the physicality of the constraints is briefly discussed, particularly in the context of quantum entanglement.
Chemical and (Photo)Catalytical Transformations in Photonic Crystal
Fibers
Matthias Schmidt, Ana M. Cubillas, Nicola Taccardi, Tijmen G. Euser, Till Cremer, Florian Maier, HansPeter Steinrueck, Philip St. J. Russell, Peter Wasserscheid, Bastian J. M. Etzold, et al.
The concept of employing photonic crystal fibers for chemical and (photo)catalytical transformations is presented. These optofluidic microdevices represent a versatile platform where light and fluids can interact for spectroscopic or photoactivation purposes. The use of photonic crystal fibers in chemistry and sensing is reviewed and recent applications as catalytic microreactors are presented. Results on homogeneous catalysis and the immobilization of homogeneous and heterogeneous catalysts in the fiber channels are discussed. The examples demonstrate that combining catalysis and the excellent light guidance of photonic crystal fibers provides unique features for example, for photocatalytic activation and quantitative photospectroscopic reaction analysis.
Fivering hollowcore photonic crystal fiber with 1.8 dB/km loss
M. H. Frosz, J. Nold, T. Weiss, A. Stefani, F. Babic, S. Rammler, P. St. J. Russell
A 19cell hollowcore photonic crystal fiber reaching 1.8 +/ 0.5 dB/km loss at 1530 nm is reported. Despite expanded corner holes in the first ring adjacent to the core, and only five cladding rings, the minimum loss is close to the previously published record of 1.7 dB/km at a comparable wavelength, achieved in a fiber with seven cladding rings. Since each additional cladding ring requires a significant increase in fabrication time and complexity, it is highly desirable to use as few as possible while still achieving low loss. Modeling results confirm that further reducing cladding deformations would yield only a small decrease in loss. This demonstrates that loss comparable to the previously demonstrated lowestloss bandgap fibers can be achieved with fiber structures that are significantly simpler and faster to fabricate. (C) 2013 Optical Society of America
Radially and Azimuthally Polarized Non Paraxial Bessel Beams
M. Ornigotti, A. Aiello
2013 CONFERENCE ON LASERS AND ELECTROOPTICS PACIFIC RIM (CLEOPR)
(2013)
We present a method for the realization of cylindrically polarized nonparaxial beams by constructing exact vector solutions of Maxwell's equations from scalar Bessel beams and combining them together by analogy with the paraxial case.
Modulation instability in the subcycle regime
Francesco Tani, John C. Travers, Philip St. J. Russell
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Cryogenic localization of single molecules with Angstrom precision
Siegfried Weisenburger, Bo Jing, Alois Renn, Vahid Sandoghdar
The precision in localizing a molecule is ultimately determined by the number of detected photons, which is in turn limited by photobleaching. Currently, fluorophores can be routinely localized to a few tens of nanometers at room temperature. In this work we demonstrate localization precision better than 3 Angstrom by substantial improvement of the molecular photostability at cryogenic temperatures. We discuss the challenges, solutions and promise of our methodology for highperformance colocalization and superresolution microscopy.
Passive modelocking of fiber ring laser at the 337th harmonic using
gigahertz acoustic core resonances
M. S. Kang, N. Y. Joly, P. St. J. Russell
OPTICS LETTERS
38(4)
561563
(2013)
We report the experimental demonstration of a passively modelocked Erdoped fiber ring laser operating at the 337th harmonic (1.80 GHz) of the cavity. The laser makes use of highly efficient Ramanlike optoacoustic interactions between the guided light and gigahertz acoustic resonances trapped in the micronsized solid glass core of a photonic crystal fiber. At sufficient pump power levels the laser output locks to a repetition rate corresponding to the acoustic frequency. A stable optical pulse train with a sidemode suppression ratio higher than 45 dB was obtained at low pump powers (similar to 60 mW). (C) 2013 Optical Society of America
Midinfrared supercontinuum generation in As2S3silica "nanospike"
stepindex waveguide
N. Granzow, M. A. Schmidt, W. Chang, L. Wang, Q. Coulombier, J. Troles, P. Toupin, I. Hartl, K. F. Lee, M. E. Fermann, et al.
Efficient generation of a broadband midinfrared supercontinuum spectrum is reported in an arsenic trisulphide waveguide embedded in silica. A chalcogenide "nanospike", designed to transform the incident light adiabatically into the fundamental mode of a 2mmlong uniform section 1 mu m in diameter, is used to achieve high launch efficiencies. The nanospike is fully encapsulated in a fused silica cladding, protecting it from the environment. Nanospikes provide a convenient means of launching light into subwavelength scale waveguides. Ultrashort (65 fs, repetition rate 100 MHz) pulses at wavelength 2 mu m, delivered from a Tmdoped fiber laser, are launched with an efficiency similar to 12% into the subwavelength chalcogenide waveguide. Soliton fission and dispersive wave generation along the uniform section result in spectral broadening out to almost 4 mu m for launched energies of only 18 pJ. The spectrum generated will have immediate uses in metrology and infrared spectroscopy. (C) 2013 Optical Society of America
Ultrafast interband nonlinear dynamics of surface plasmon polaritons in
gold nanowires
Andrea Marini, Matteo Conforti, Giuseppe Della Valle, Fabio Biancalana
Conference on Lasers and ElectroOptics
(2013)
We theoretically model the nonlinear dynamics of plasmonic waves in gold nanowires. We find that the thermomodulational nonlinearity of gold leads to a strong spectral redshift of input pulses in a few microns of propagation. (C) 2013 Optical Society of America
Nonclassical features of the polarization quasiprobability distribution
Polarization quasiprobability distribution is defined in the space of the Stokes observables. It can be reconstructed with the help of polarization quantum tomography and provides a full description of the socalled polarization sector of quantum states of light. We show here that due to its definition in terms of the discretevalued Stokes operators, polarization quasiprobability distribution has singularities at integer values of the Stokes observables and takes negative values even for the quantum states typically considered as "classical" ones. In experiments with "bright" multiphoton states, the photonnumber resolution is smeared due to the photodetectors' technical limitations. In this case, nonclassical features of the explored quantum states can be revealed by adding a strong coherent beam into the orthogonal polarization.
We present a method for implementing a weak optical Kerr interaction (singlemode Kerr Hamiltonian) in a measurementbased fashion using the common set of universal elementary interactions for continuousvariable quantum computation. Our scheme is a conceptually distinct alternative to the use of naturally occurring, weak Kerr nonlinearities or specially designed nonlinear media. Instead, we propose to exploit suitable offline prepared quartic ancilla states together with beam splitters, squeezers, and homodyne detectors. For perfect ancilla states and ideal operations, our decompositions for obtaining the measurementbased Kerr Hamiltonian lead to a realization with nearunit fidelity. Nonetheless, even by using only approximate ancilla states in the form of superposition states of up to four photons, high fidelities are still attainable. Our scheme requires four elementary operations and its deterministic implementation corresponds to about 10 ancillabased gate teleportations. We test our measurementbased Kerr interaction against an ideal Kerr Hamiltonian by applying them both to weak coherent states and singlephoton superposition states.
QED with a parabolic mirror
G. Alber, J. Z. Bernad, M. Stobinska, L. L. SanchezSoto, G. Leuchs
We investigate the quantum electrodynamics of a single twolevel atom located at the focus of a parabolic cavity. We first work out the modifications of the spontaneous emission induced by the presence of this boundary in the optical regime, where the dipole and the rotatingwave approximations apply. Furthermore, the singlephoton state that leaves the cavity asymptotically is determined. The corresponding timereversed singlephoton quantum state is capable of exciting the atom in this extreme multimode scenario with nearunit probability. Using semiclassical methods, we derive a photonpath representation for the relevant transition amplitudes and show that it constitutes a satisfactory approximation for a wide range of wavelengths.
Towards a microscopic description of the optical nonlinearities of
goldbased plasmonic devices
Andrea Marini, Fabio Biancalana
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Corrections to the knifeedge based reconstruction scheme of tightly
focused light beams
The knifeedge method is an established technique for profiling light beams. It was shown, that this technique even works for tightly focused beams, if the material and geometry of the probing knifeedges are chosen carefully. Furthermore, it was also reported recently that this method fails, when the knifeedges are made from pure materials. The artifacts introduced in the reconstructed beam shape and position depend strongly on the edge and input beam parameters, because the knifeedge is excited by the incoming beam. Here we show, that the actual beam shape and spot size of tightly focused beams can still be derived from knifeedge measurements for pure edge materials and different edge thicknesses by adapting the analysis method of the experimental data taking into account the interaction of the beam with the edge. (C) 2013 Optical Society of America
Applying contact to individual silicon nanowires using a
dielectrophoresis (DEP)based technique
Christian Leiterer, Gerald Broenstrup, Norbert Jahr, Matthias Urban, Cornelia Arnold, Silke Christiansen, Wolfgang Fritzsche
JOURNAL OF NANOPARTICLE RESEARCH
15(5)
1628
(2013)

Journal
One major challenge for the technological use of nanostructures is the control of their electrical and optoelectronic properties. For that purpose, extensive research into the electrical characterization and therefore a fast and reliable way of contacting these structures are needed. Here, we report on a new, dielectrophoresis (DEP)based technique, which enables to apply sufficient and reliable contact to individual nanostructures, like semiconducting nanowires (NW), easily and without the need for lithography. The DEP contacting technique presented in this article can be done without hightech equipment and monitored in situ with an optical microscope. In the presented experiments, individual SiNWs are trapped and subsequently welded between two photolithographically prepatterned electrodes by applying varying AC voltages to the electrodes. To proof the quality of these contacts, IV curves, photoresponse and photoconductivity of a single SiNW were measured. Furthermore, the measured photoconductivity in dependence on the wavelength of illuminated light and was compared with calculations predicting the absorption spectra of an individual SiNW.
Towards an Entropic Analysis of Quantum Error Correction with
Imperfections
The concept of entropy and the correct application of the Second Law of thermodynamics are essential in order to understand the reason why quantum error correction (QEC) is thermodynamically possible and no violation of the Second Law occurs during its execution.
We report here on our preliminary work aiming at an informationtheoretic analysis extended to QEC in the presence of imperfections.
Radially and azimuthally polarized nonparaxial Bessel beams made simple
We present a method for the realization of radially and azimuthally polarized nonparaxial Bessel beams in a rigorous but simple manner. This result is achieved by using the concept of Hertz vector potential to generate exact vector solutions of Maxwell's equations from scalar Bessel beams. The scalar part of the Hertz potential is built by analogy with the paraxial case as a linear combination of Bessel beams carrying a unit of orbital angular momentum. In this way we are able to obtain spatial and polarization patterns analogous to the ones exhibited by the standard cylindrically polarized paraxial beams. Applications of these beams are discussed. (C) 2013 Optical Society of America
A goldnanotip optical fiber for plasmonenhanced nearfield detection
P. Uebel, S. T. Bauerschmidt, M. A. Schmidt, P. St. J. Russell
A wetchemical etching and mechanical cleaving technique is used to fabricate gold nanotips attached to tapered optical fibers. Localized surface plasmon resonances (tunable from 500 to 850 nm by varying the tip dimensions) are excited at the tip, and the signal is transmitted via the fiber to an optical analyzer, making the device a plasmonenhanced nearfield probe. A simple cavity model is used to explain the resonances observed in numerical simulations. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
All Photons are Equal but Some Photons are More Equal Than Others
F. Toeppel, A. Aiello, G. Leuchs
2013 CONFERENCE ON LASERS AND ELECTROOPTICS PACIFIC RIM (CLEOPR)
(2013)
Two photons are identical if they are prepared in the same quantum state and there is a unique way to achieve this. Conversely, there are many different ways of preparing two nonidentical photons: they may differ in polarization, frequency, modefunction, etc. Thus, photon distinguishability depends upon the degree of freedom being varied. By analyzing the coincidence probability distribution in a HongOuMandel experiment, we show that photon distinguishability can be quantified by the rate of distinguishability of photons, an experimentally measurable parameter that crucially depends on both the photonquantum state and the degree of freedom under control.
From Arrays of THz Antennas to LargeArea Emitters
Gottfried H. Doehler, Luis Enrique GarciaMunoz, Sascha Preu, Stefan Malzer, Sebastian Bauerschmidt, Javier MonterodePaz, Eduardo UgarteMunoz, Alejandro RiveraLavado, Vicente GonzalezPosadas, Daniel SegoviaVargas, et al.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
3(5)
532544
(2013)

Journal
Arrays of coherently driven photomixers with antenna (antenna emitter arrays, AEAs) have been evaluated as a possibility to overcome the power limitations of individual conventional photomixers with antenna ("antenna emitters", AEs) for the generation of continuouswave (CW) THz radiation. In this paper, "large area emitters" (LAEs) are proposed as an alternative approach, and compared with AEAs. In this antennafree new scheme of photomixing, the THz radiation originates directly from the acceleration of photoinduced charge carriers generated within a large semiconductor area. The quasicontinuous distribution of emitting elements corresponds to a highdensity array and results in favorable radiation profiles without side lobes. Moreover, the achievable THz power is expected to outnumber even large AEAs. Last not least, the technological challenge of fabricating LAEs appears to be significantly less demanding.
Geometrical aspects of PTinvariant transfer matrices
J. J. Monzon, A. G. Barriuso, J. M. MontesinosAmilibia, L. L. SanchezSoto
We show that the transfer matrix for a PTinvariant system, when recast in the appropriate variables, can be interpreted as a point in the (3 + 1)dimensional de Sitter space. We introduce a natural PTinvariant composition law for these matrices and confirm that their action appears as a Lorentz transformation. We elucidate the geometrical meaning of the PT symmetry breaking and suggest that the cosmological event horizon arising in the de Sitter metric can be can be unraveled with a simple optical scheme. DOI: 10.1103/PhysRevA.87.012111
Formation of quartic solitons in siliconbased slot waveguides
Samudra Roy, Fabio Biancalana
Conference on Lasers and ElectroOptics
(2013)
We investigate the possibility to excite the socalled quartic solitons (QS) in specially designed silicon based slot waveguides. The proposed waveguides exhibit ideal dispersion profile and realistic operational conditions to support true QS.
Formation of quartic solitons and a localized continuum in siliconbased
slot waveguides
We explore the possibility of exciting the socalled quartic solitons in specially designed slot waveguides based on silicon and silica or silicon nanocrystals. This requires the excitation of the structure with quasitransversemagnetic polarized pulsesfor which the Raman effect is absentand at a specific infrared wavelength for which only the second and fourthorder group velocity coefficients are nonvanishing. Pulses launched in these conditions will generate a spectrally localized continuum coming from the spectral interference of many quartic solitons. DOI: 10.1103/PhysRevA.87.025801
Visualizing Multiphase Flow and Trapped Fluid Configurations in a Model
ThreeDimensional Porous Medium
Amber T. Krummel, Sujit S. Datta, Stefan Muenster, David A. Weitz
We report an approach to fully visualize the flow of two immiscible fluids through a model threedimensional (3D) porous medium at porescale resolution. Using confocal microscopy, we directly image the drainage of the medium by the nonwetting oil and subsequent imbibition by the wetting fluid. During imbibition, the wetting fluid pinches off threads of oil in the narrow crevices of the medium, forming disconnected oil ganglia. Some of these ganglia remain trapped within the medium. By resolving the full 3D structure of the trapped ganglia, we show that the typical ganglion size, as well as the total amount of residual oil, decreases as the capillary number Ca increases; this behavior reflects the competition between the viscous pressure in the wetting fluid and the capillary pressure required to force oil through the pores of the medium. This work thus shows how porescale fluid dynamics influence the trapped fluid configurations in multiphase flow through 3D porous media. (C) 2013 American Institute of Chemical Engineers AIChE J, 59: 10221029, 2013
Longdistance laser propulsion and deformationmonitoring of cells in
optofluidic photonic crystal fiber
Sarah Unterkofler, Martin K. Garbos, Tijmen G. Euser, Philip St. J. Russell
JOURNAL OF BIOPHOTONICS
6(9)
743752
(2013)

Journal
We introduce a unique method for laserpropelling individual cells over distances of 10s of cm through stationary liquid in a microfluidic channel. This is achieved by using liquidfilled hollowcore photonic crystal fiber (HCPCF). HCPCF provides lowloss light guidance in a welldefined single mode, resulting in highly uniform optical trapping and propulsive forces in the core which at the same time acts as a microfluidic channel. Cells are trapped laterally at the center of the core, typically several microns away from the glass interface, which eliminates adherence effects and external perturbations. During propagation, the velocity of the cells is conveniently monitored using a nonimaging Doppler velocimetry technique. Dynamic changes in velocity at constant optical powers up to 350 mW indicate stressinduced changes in the shape of the cells, which is confirmed by brightfield microscopy. Our results suggest that HCPCF will be useful as a new tool for the study of singlecell biomechanics. ((c) 2013 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim)
Complex polarization in non zcut whispering gallery mode resonators
F. Sedlmeir, M. Hauer, J. Fuerst, D. V. Strekalov, H. G. L. Schwefel
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Measurementinduced amplification of optical catlike states
A. Laghaout, J. S. NeergaardNielsen, J. Rigas, C. Kragh, A. Tipsmark, U. L. Andersen
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Dynamical generation of interwoven soliton trains by nonlinear emission
in binary BoseEinstein condensates
We propose a method for the generation of trains of alternating bright solitons in twocomponent BoseEinstein condensates, using controlled emission of nonlinear matter waves in the uncoupled regime with spatially varying intraspecies interaction and outofphase oscillations of the ground states in the trap. Under this scheme, solitons are sequentially launched from the different components and interact with each other through phaseindependent cross coupling. We obtain an analytical estimation of the critical condition for soliton emission using a geometric guiding model, in analogy with integrated optical systems. In addition, we show how strong initial perturbations in the system can trigger the spontaneous generation of supersolitons, i.e., localized phononlike excitations of the soliton trains. Finally, we demonstrate the controllable generation of slow and fast supersolitons by adding external localized potentials in the nonlinear region.
Nonlinear optics in Xefilled hollowcore PCF in high pressure and
supercritical regimes
M. Azhar, N. Y. Joly, J. C. Travers, P. St J. Russell
APPLIED PHYSICS BLASERS AND OPTICS
112(4)
457460
(2013)

Journal
Supercritical Xe at 293 K offers a Kerr nonlinearity that can exceed that of fused silica while being free of Raman scattering. It also has a much higher optical damage threshold and a transparency window that extends from the UV to the infrared. We report the observation of nonlinear phenomena, such as selfphase modulation, in hollowcore photonic crystal fiber filled with supercritical Xe. In the subcritical regime, intermodal fourwave mixing resulted in the generation of UV light in the HE12 mode. The normal dispersion of the fiber at high pressures means that spectral broadening can be clearly obtained without influence from soliton effects or material damage.
Arrayed free space continuouswave terahertz photomixers
S. T. Bauerschmidt, G. H. Doehler, H. Lu, A. C. Gossard, S. Malzer, S. Preu
We present free space coherent arrays of continuouswave terahertz (THz) photomixers and compare the results to onchip arrays. By altering the relative phases of the exciting laser signals, the relative THz phase between the array elements can be tuned, allowing for beam steering. In addition, the constructive interference of the emission of N elements leads to an increase of the focal intensity by a factor of N2 while reducing the beam width by similar to N1, below the diffraction limit of a single source. Such array architectures strongly improve the THz power distribution for standoff spectroscopy and imaging systems while providing a huge bandwidth at the same time. We demonstrate this by beam profiles generated by a 2 x 2 and a 4 x 1 array for a transmission distance of 4.2 m. Spectra between 70 GHz and 1.1 THz have been recorded with these arrays. (C) 2013 Optical Society of America
Quantum repeaters and quantum key distribution: Analysis of secretkey
rates
Silvestre Abruzzo, Sylvia Bratzik, Nadja K. Bernardes, Hermann Kampermann, Peter van Loock, Dagmar Bruss
We analyze various prominent quantum repeater protocols in the context of longdistance quantum key distribution. These protocols are the original quantum repeater proposal by Briegel, Dur, Cirac and Zoller, the socalled hybrid quantum repeater using optical coherent states dispersively interacting with atomic spin qubits, and the DuanLukinCiracZollertype repeater using atomic ensembles together with linear optics and, in its most recent extension, heralded qubit amplifiers. For our analysis, we investigate the most important experimental parameters of every repeater component and find their minimally required values for obtaining a nonzero secret key. Additionally, we examine in detail the impact of device imperfections on the final secret key rate and on the optimal number of rounds of distillation when the entangled states are purified right after their initial distribution.
Optical diametric drive acceleration through actionreaction symmetry
breaking
Martin Wimmer, Alois Regensburger, Christoph Bersch, MohammadAli Miri, Sascha Batz, Georgy Onishchukov, Demetrios N. Christodoulides, Ulf Peschel
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(1). In such a hypothetical arrangement, two interacting particles constantly accelerate each other in the same direction through a violation of the actionreaction 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(27). Here we report the first experimental observation of such diametric drive acceleration for pulses propagating in a nonlinear optical mesh lattice(814). The demonstrated reversal of actionreaction symmetry could enable altogether new possibilities for frequency conversion and pulsesteering applications.
Stokes vector based polarization resolved second harmonic microscopy of
starch granules
Nirmal Mazumder, Jianjun Qiu, Matthew R. Foreman, Carlos Macias Romero, Peter Toeroek, FuJen Kao
BIOMEDICAL OPTICS EXPRESS
4(4)
538547
(2013)
We report on the measurement and analysis of the polarization state of second harmonic signals generated by starch granules, using a fourchannel photon counting based Stokespolarimeter. Various polarization parameters, such as the degree of polarization (DOP), the degree of linear polarization (DOLP), the degree of circular polarization (DOCP), and anisotropy are extracted from the 2D second harmonic Stokes images of starch granules. The concentric shell structure of a starch granule forms a natural photonic crystal structure. By integration over all the solid angle, it will allow very similar SHG quantum efficiency regardless of the angle or the states of incident polarization. Given type I phase matching and the concentric shell structure of a starch granule, one can easily infer the polarization states of the input beam from the resulting SH micrograph. (C) 2013 Optical Society of America
Diffractive Resonant Radiation Emitted by Spatial Solitons in Waveguide
Arrays
We study analytically and numerically the diffractive resonant radiation emitted by spatial solitons, which is generated in waveguide arrays with Kerr nonlinearity. The phase matching condition between solitons and radiation is derived and studied for the first time and agrees well with direct pulse propagation simulations. The folded dispersion due to the Brillouin zone leads to a peculiar anomalous soliton recoil that we describe in detail. DOI: 10.1103/PhysRevLett.110.113903
Whispering gallery modes at the rim of an axisymmetric optical
resonator: Analytical versus numerical description and comparison with
experiment
I. Breunig, B. Sturman, F. Sedlmeir, H. G. L. Schwefel, K. Buse
Optical whispering gallery modes (WGMs) of mmsized axisymmetric resonators are well localized at the equator. Employing this distinctive feature, we obtain simple analytical relations for the frequencies and eigenfunctions of WGMs which include the major radius of the resonator and the curvature radius of the rim. Being compared with results of finiteelement simulations, these relations show a high accuracy and practicability. Highprecision freespectralrange measurements with a millimetersized disc resonator made of MgF2 allow us to identify the WGMs and confirm the applicability of our analytical description. (C) 2013 Optical Society of America
Efficient antiStokes generation via intermodal stimulated Raman
scattering in gasfilled hollowcore PCF
B. M. Trabold, A. Abdolvand, T. G. Euser, P. St J. Russell
A strong antiStokes Raman signal, from the vibrational Q(1) transition of hydrogen, is generated in gasfilled hollowcore photonic crystal fiber. To be efficient, this process requires phasematching, which is not automatically provided since the group velocity dispersion is typically nonzero andinside a fibercannot be compensated for using a crossedbeam geometry. Phasematching can however be arranged by exploiting the different dispersion profiles of higherorder modes. We demonstrate the generation of first and second antiStokes signals in higherorder modes by pumping with an appropriate mixture of fundamental and a higherorder modes, synthesized using a spatial light modulator. Conversion efficiencies as high as 5.3% are achieved from the pump to the first antiStokes band. (C) 2013 Optical Society of America
Causal signal transmission by quantum fields. VI: The Lorentz condition
and Maxwell's equations for fluctuations of the electromagnetic field
The general structure of electromagnetic interactions in the socalled response representation of quantum electrodynamics (QED) is analysed. A formal solution to the general quantum problem of the electromagnetic field interacting with matter is found. Independently, a formal solution to the corresponding problem in classical stochastic electrodynamics (CSED) is constructed. CSED and QED differ only in the replacement of stochastic averages of cnumber fields and currents by timenormal averages of the corresponding Heisenberg operators. All relations of QED connecting quantum field to quantum current lack Planck's constant, and thus coincide with their counterparts in CSED. In Feynman's terms, one encounters complete disentanglement of the potential and current operators in response picture.
Based on this parallelism between QED and CSED, it is natural to expect validity of the Lorentz condition and Maxwell's equations for the timenormal averages of the potential and current. Things however turn out to be more complicated. Maxwell's equations under the timenormal ordering can only be demonstrated subject to cancellation of the socalled Schwinger terms by gaugeinvariant regularisations. We presume this pattern to be general, formulating this as "commutativity conjecture". Consistency of the latter with the Heisenberg uncertainty principle is discussed. (C) 2013 Elsevier Inc. All rights reserved.
Grapheneclad tapered fiber: effective nonlinearity and propagation
losses
We derive a pulse propagation equation for a grapheneclad optical fiber, treating the optical response of the graphene and nonlinearity of the dielectric fiber core as perturbations in asymptotic expansion of Maxwell equations. We analyze the effective nonlinear and attenuation coefficients due to the graphene layer. Based on the recent experimental measurements of the nonlinear graphene conductivity, we predict considerable enhancement of the effective nonlinearity for subwavelength fiber core diameters. (C) 2013 Optical Society of America
Finite element simulation of a perturbed axialsymmetric
whisperinggallery mode and its use for intensity enhancement with a
nanoparticle coupled to a microtoroid
Alex Kaplan, Matthew Tomes, Tal Carmon, Maxim Kozlov, Oren Cohen, Guy Bartal, Harald G. L. Schwefel
We present an optical mode solver for a whispering gallery resonator coupled to an adjacent arbitrary shaped nanoparticle that breaks the axial symmetry of the resonator. Such a hybrid resonatornanoparticle is similar to what was recently used for biodetection and for field enhancement. We demonstrate our solver by parametrically studying a toroidnanoplasmonic device and get the optimal nanoplasmonic size for maximal enhancement. We investigate cases near a plasmonic resonance as well as far from a plasmonic resonance. Unlike common plasmons that typically benefit from working near their resonance, here working far from plasmonic resonance provides comparable performance. This is because the plasmonic resonance enhancement is accompanied by cavity quality degradation through plasmonic absorption. (C) 2013 Optical Society of America
Optoacoustic isolators in photonic crystal fibre
A. Butsch, M. S. Kang, P. St J. Russell
2013 IEEE PHOTONICS SOCIETY SUMMER TOPICAL MEETING SERIES
212213
(2013)
Coherent opticallydriven GHz acoustic waves, tightly guided in the micronsized core of photonic crystal fibre, enable reconfigurable dynamic optical isolation and switching, providing new functionality that is useful in various types of alloptical fibre systems.
Experimental characterization of an uniaxial angle cut whispering
gallery mode resonator
Florian Sedlmeir, Martin Hauer, Josef U. Fuerst, Gerd Leuchs, Harald G. L. Schwefel
The usual configuration of uniaxial whispering gallery mode resonators is a disk shaped geometry where the optic axis points along the symmetry axis, a so called zcut resonator. Recently xcut resonators, where the optic axis lies in the equatorial plane, became of interest as they enable extremely broadband second harmonic generation. In this paper we report on the properties of a more generalized system, the so called anglecut resonator, where the optic axis exhibits an arbitrary angle against the symmetry axis. We show experimentally that the modal structure and quality factors are similar to common resonators but that the polarization properties differ quite significantly: due to the asymmetry the polarization depends on the equatorial position and is, in general, elliptical. (C) 2013 Optical Society of America
Improved efficiency of photoconductive THz emitters by increasing the effective contact length of electrodes
Abhishek Singh, Harshad Surdi, V. V. Nikesh, S. S. Prabhu, G. H. Doehler
We study the effect of a surface modification at the interface between metallic electrodes and semiconducting substrate in SemiInsulating GaAs (SIGaAs) based photoconductive emitters (PCE) on the emission of TeraHertz (THz) radiation. We partially etch out a 500 nm thick layer of SIGaAs in grating like pattern with various periods before the contact deposition. By depositing the electrodes on the patterned surface, the electrodes follow the contour of the grating period. This increases the effective contact length of the electrodes per unit area of the active regions on the PCE. The maxima of the electric field amplitude of the THz pulses emitted from the patterned surface are enhanced by up to more than a factor 2 as compared to an unpatterned surface. We attribute this increase to the increase of the effective contact length of the electrode due to surface patterning. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
The effect of LandauZener dynamics on phonon lasing
Huaizhi Wu, Georg Heinrich, Florian Marquardt
New Journal of Physics
15
123022
(2013)

Journal

PDF
Optomechanical systems couple light to the motion of nanomechanical objects. Intriguing new effects are observed in recent experiments that involve the dynamics of more than one optical mode. There, mechanical motion can stimulate strongly driven multimode photon dynamics that acts back on the mechanics via radiation forces. We show that even for two optical modes LandauZenerStueckelberg oscillations of the light field drastically change the nonlinear attractor diagram of the resulting phonon lasing oscillations. Our findings illustrate the generic effects of LandauZener physics on backaction induced selfoscillations.
Observing the Nonequilibrium Dynamics of the Quantum TransverseField Ising Chain in Circuit QED
Oliver Viehmann, Jan von Delft, Florian Marquardt
Physical Review Letters
110(3)
030601
(2013)

Journal

PDF
We show how a quantum Ising spin chain in a timedependent transverse magnetic field can be simulated and experimentally probed in the framework of circuit QED with current technology. The proposed setup provides a new platform for observing the nonequilibrium dynamics of interacting manybody systems. We calculate its spectrum to offer a guideline for its initial experimental characterization. We demonstrate that quench dynamics and the propagation of localized excitations can be observed with the proposed setup and discuss further possible applications and modifications of this circuit QED quantum simulator. DOI: 10.1103/PhysRevLett.110.030601
Simulating singlephotonsingleatom absorption experiments with an
optical resonator
Marianne Bader, Simon Heugel, Alexander Chekhov, Markus Sondermann, Gerd Leuchs
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Mimicking the nonlinear dynamics of optical fibers with waveguide
arrays: towards a spatiotemporal supercontinuum generation
We numerically demonstrate the formation of the spatiotemporal version of the socalled diffractive resonant radiation generated in waveguide arrays with Kerr nonlinearity when a long pulse is launched into the system. The phase matching condition for the diffractive resonant radiation that we have found earlier for CW beams also works well in the spatiotemporal case. By introducing a linear potential, one can introduce a continuous shift of the central wavenumber of a linear pulse, whereas in the nonlinear case one can demonstrate that the soliton selfwavenumber shift can be compensated by the emission of diffractive resonant radiation, in a very similar fashion as it is done in optical fibers. This work paves the way for designing unique optical devices that generate spectrally broad supercontinua with a controllable directionality by taking advantage of the combined physics of optical fibers and waveguide arrays. (C) 2013 Optical Society of America
Total absorption of light by a nanoparticle: an electromagnetic sink in
the optical regime
A. Sentenac, P. C. Chaumet, G. Leuchs
OPTICS LETTERS
38(6)
818820
(2013)
In this Letter, we give a general description of the illumination and object properties for obtaining total absorption. We show theoretically and numerically that properly designed sub100 nm metallic particles are able to absorb all the energy of an incident beam if the latter is adequately shaped. In addition to their interest as absorbers, these particles act as efficient nearfield probes as they convert the incident propagating beam into a localized nonradiative field. (C) 2013 Optical Society of America
Spectrofluorimetry with attomole sensitivity in photonic crystal fibres
Gareth O. S. Williams, Tijmen G. Euser, Philip St J. Russell, Anita C. Jones
METHODS AND APPLICATIONS IN FLUORESCENCE
1(1)
(2013)

Journal
We report the use of photonic crystal fibres (PCF) as spectrofluorimetric systems in which sample solutions are excited within the microstructure of the fibre. The use of intrafibre excitation has several advantages that combine to enable highly sensitive measurements of fluorescence spectra and lifetimes: long pathlengths are achieved by the efficient guidance of the fundamental mode; sample volumes contained within the micronscale structure are very small, only a few nanolitres per cm of path; collection and guidance of the emitted fluorescence is efficient and the fluorescence lifetime is unperturbed. Fluorophores in bulk solution can be studied in hollow core PCF, whereas the use of PCF with a suspended, solid core enables selective excitation of molecules in close proximity to the silica surface, through interaction with the evanescent field. We demonstrate the measurement of fluorescence spectra and fluorescence lifetimes in each of these excitation regimes and report the detection of attomole quantities of fluorescein.
Material Properties of LaserWelded Thin Silicon Foils
M. T. Hessmann, T. Kunz, M. Voigt, K. Cvecek, M. Schmidt, A. Bochmann, S. Christiansen, R. Auer, C. J. Brabec
INTERNATIONAL JOURNAL OF PHOTOENERGY
724502
(2013)

Journal
An extended monocrystalline silicon base foil offers a great opportunity to combine lowcost production with high efficiency silicon solar cells on a large scale. By overcoming the area restriction of ingotbased monocrystalline silicon wafer production, costs could be decreased to thin film solar cell range. The extended monocrystalline silicon base foil consists of several individual thin silicon wafers which are welded together. A comparison of three different approaches to weld 50 mu m thin silicon foils is investigated here: (1) laser spot welding with low constant feed speed, (2) laser line welding, and (3) keyhole welding. Crosssections are prepared and analyzed by electron backscatter diffraction (EBSD) to reveal changes in the crystal structure at the welding side after laser irradiation. The treatment leads to the appearance of new grains and boundaries. The induced internal stress, using the three different laser welding processes, was investigated by microRaman analysis. We conclude that the keyhole welding process is the most favorable to produce thin silicon foils.
A versatile source of single photons for quantum information processing
Michael Foertsch, Josef U. Fuerst, Christoffer Wittmann, Dmitry Strekalov, Andrea Aiello, Maria V. Chekhova, Christine Silberhorn, Gerd Leuchs, Christoph Marquardt
The generation of highquality singlephoton states with controllable narrow spectral bandwidths and central frequencies is key to facilitate efficient coupling of any atomic system to nonclassical light fields. Such an interaction is essential in numerous experiments for fundamental science and applications in quantum communication and information processing, as well as in quantum metrology. Here we implement a fully tunable, narrowband and efficient singlephoton source based on a whispering gallery mode resonator. Our diskshaped, monolithic and intrinsically stable resonator is made of lithium niobate and supports a cavityassisted spontaneous parametric downconversion process. The generated photon pairs are emitted into two highly tunable resonator modes. We verify wavelength tuning over 100 nm of both modes with controllable bandwidth between 7.2 and 13 MHz. Heralding of single photons yields antibunching with g((2))(0) < 0.2.
Spectral broadening in Brillouin imaging
Giuseppe Antonacci, Matthew R. Foreman, Carl Paterson, Peter Toeroek
Brillouin microscopy is an emerging imaging modality that provides fundamental information about mechanical properties of media in a noncontact manner. To date, low numerical aperture (NA) optics have been used, due to noticeable angular broadening of the Brillouin spectrum at higher NAs. In this work, we investigate theoretically and experimentally the dependence of spectral broadening effects in Brillouin imaging on system NA, for both 90 degrees and 180 degrees scattering geometries. Lineshape deformations and broadening are found to be minimised in a backscattering geometry, hence paving the way for high resolution invivo mechanical imaging. (C) 2013 AIP Publishing LLC.
Rydberg Spectroscopy in HollowCore Photonic Crystal Fiber
G. Epple, K. Kleinbach, T. G. Euser, R. Loew, P. St J. Russell
Conference on Lasers and ElectroOptics
(2013)
We present the first roomtemperature results on a threephoton excitation of Rydberg states in cesium atoms placed inside a kagomestyle hollowcore photonic crystal fiber.
PhasePreserving Amplitude Regeneration of a TwoAmplitudeLevel
Modulation Format
Tobias Roethlingshoefer, Thomas Richter, Colja Schubert, Georgy Onishchukov, Bernhard Schmauss, Gerd Leuchs
2013 CONFERENCE ON LASERS AND ELECTROOPTICS PACIFIC RIM (CLEOPR)
(2013)
It has been experimentally shown that a modified nonlinear loop mirror can be used for alloptical star8QAM processing. An amplitude noise reduction of 2.2 dB could be demonstrated for the highpower states.
Polariton excitation in epsilonnearzero slabs: Transient trapping of
slow light
Alessandro Ciattoni, Andrea Marini, Carlo Rizza, Michael Scalora, Fabio Biancalana
We numerically investigate the propagation of a spatially localized and quasimonochromatic electromagnetic pulse through a slab with a Lorentz dielectric response in the epsilonnearzero regime, where the real part of the permittivity vanishes at the pulse carrier frequency. We show that the pulse is able to excite a set of virtual polariton modes supported by the slab, with the excitation undergoing a generally slow damping due to absorption and radiation leakage. Our numerical and analytical approaches indicate that in its transient dynamics the electromagnetic field displays the very same enhancement of the field component perpendicular to the slab, as in the monochromatic regime. The transient trapping is inherently accompanied by a significantly reduced group velocity ensuing from the small dielectric permittivity, thus providing an alternative platform for achieving control and manipulation of slow light.
Photonic crystal fibres for chemical sensing and photochemistry
Ana M. Cubillas, Sarah Unterkofler, Tijmen G. Euser, Bastian J. M. Etzold, Anita C. Jones, Peter J. Sadler, Peter Wasserscheid, Philip St. J. Russell
CHEMICAL SOCIETY REVIEWS
42(22)
86298648
(2013)

Journal
In this review, we introduce photonic crystal fibre as a novel optofluidic microdevice that can be employed as both a versatile chemical sensor and a highly efficient microreactor. We demonstrate that it provides an excellent platform in which light and chemical samples can strongly interact for quantitative spectroscopic analysis or photoactivation purposes. The use of photonic crystal fibre in photochemistry and sensing is discussed and recent results on gas and liquid sensing as well as on photochemical and catalytic reactions are reviewed. These developments demonstrate that the tight light confinement, enhanced lightmatter interaction and reduced sample volume offered by photonic crystal fibre make it useful in a wide range of chemical applications.
Amplification of higherorder modes by stimulated Raman scattering in
H2filled hollowcore photonic crystal fiber
B. M. Trabold, A. Abdolvand, T. G. Euser, A. M. Walser, P. St. J. Russell
OPTICS LETTERS
38(5)
600602
(2013)
We report a method for amplifying higherorder guided modes, synthesized with a spatial light modulator, in a hydrogenfilled hollowcore photonic crystal fiber. The gain mechanism is intermodal stimulated Raman scattering, a pump laser source in the fundamental mode providing amplification for weak higherorder seed modes at the Stokes frequency. The gain for higherorder modes up to LP31 is calculated and verified experimentally. (C) 2013 Optical Society of America
Squeezed light from a silicon micromechanical resonator
Amir H. SafaviNaeini, Simon Groeblacher, Jeff T. Hill, Jasper Chan, Markus Aspelmeyer, Oskar Painter
Monitoring a mechanical object's motion, even with the gentle touch of light, fundamentally alters its dynamics. The experimental manifestation of this basic principle of quantum mechanics, its link to the quantum nature of light and the extension of quantum measurement to the macroscopic realm have all received extensive attention over the past halfcentury(1,2). The use of squeezed light, with quantum fluctuations below that of the vacuum field, was proposed nearly three decades ago(3) as a means of reducing the optical readout noise in precision force measurements. Conversely, it has also been proposed that a continuous measurement of a mirror's position with light may itself give rise to squeezed light(4,5). Such squeezedlight generation has recently been demonstrated in a system of ultracold gasphase atoms(6) whose centreofmass motion is analogous to the motion of a mirror. Here we describe the continuous position measurement of a solidstate, optomechanical system fabricated from a silicon microchip and comprising a micromechanical resonator coupled to a nanophotonic cavity. Laser light sent into the cavity is used to measure the fluctuations in the position of the mechanical resonator at a measurement rate comparable to its resonance frequency and greater than its thermal decoherence rate. Despite the mechanical resonator's highly excited thermal state (10(4) phonons), we observe, through homodyne detection, squeezing of the reflected light's fluctuation spectrum at a level 4.5 +/ 0.2 per cent below that of vacuum noise over a bandwidth of a few megahertz around the mechanical resonance frequency of 28 megahertz. With further device improvements, onchip squeezing at significant levels should be possible, making such integrated microscale devices well suited for precision metrology applications.
Collective Dynamics in Optomechanical Arrays
Florian Marquardt
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Spatiospectral characteristics of parametric downconversion in
waveguide arrays
R. Kruse, F. Katzschmann, A. Christ, A. Schreiber, S. Wilhelm, K. Laiho, A. Gabris, C. S. Hamilton, I. Jex, C. Silberhorn, et al.
High dimensional quantum states are of fundamental interest for quantum information processing. They give access to large Hilbert spaces and, in turn, enable the encoding of quantum information on multiple modes. One method to create such quantum states is parametric downconversion (PDC) in waveguide arrays (WGAs) which allows for the creation of highly entangled photon pairs in controlled, easily accessible spatial modes, with unique spectral properties.
In this paper we examine both theoretically and experimentally the PDC process in a lithium niobate WGA. We measure the spatial and spectral properties of the emitted photon pairs, revealing correlations between spectral and spatial degrees of freedom of the created photons. Our measurements show that, in contrast to prior theoretical approaches, spectrally dependent coupling effects have to be taken into account in the theory of PDC in WGAs. To interpret the results, we developed a theoretical model specifically taking into account spectrally dependent coupling effects, which further enables us to explore the capabilities and limitations for engineering the spatial correlations of the generated quantum states.
Level repulsion in hybrid photonicplasmonic microresonators for
enhanced biodetection
We theoretically analyze photonicplasmonic coupling between a highQ whispering gallery mode (WGM) resonator and a coreshell nanoparticle. Blue and red shifts of WGM resonances are shown to arise from crossing of the photonic and plasmonic modes. Level repulsion in the hybrid system is further seen to enable sensitivity enhancements in WGM sensors: maximal when the two resonators are detuned by half the plasmon linewidth. Approximate bounds are given to quantify possible enhancements. Criteria for reactive vs resistive coupling are also established.
Theory of quantum frequency conversion and typeII parametric
downconversion in the highgain regime
Andreas Christ, Benjamin Brecht, Wolfgang Mauerer, Christine Silberhorn
Frequency conversion (FC) and typeII parametric downconversion (PDC) processes serve as basic building blocks for the implementation of quantum optical experiments: typeII PDC enables the efficient creation of quantum states such as photonnumber states and EinsteinPodolskyRosen (EPR)states. FC gives rise to technologies enabling efficient atomphoton coupling, ultrafast pulse gates and enhanced detection schemes. However, despite their widespread deployment, their theoretical treatment remains challenging. Especially the multiphoton components in the highgain regime as well as the explicit timedependence of the involved Hamiltonians hamper an efficient theoretical description of these nonlinear optical processes. In this paper, we investigate these effects and put forward two models that enable a full description of FC and typeII PDC in the highgain regime. We present a rigorous numerical model relying on the solution of coupled integrodifferential equations that covers the complete dynamics of the process. As an alternative, we develop a simplified model that, at the expense of neglecting timeordering effects, enables an analytical solution. While the simplified model approximates the correct solution with high fidelity in a broad parameter range, sufficient for many experimental situations, such as FC with low efficiency, entangled photonpair generation and the heralding of single photons from typeII PDC, our investigations reveal that the rigorous model predicts a decreased performance for FC processes in quantum pulse gate applications and an enhanced EPRstate generation rate during typeII PDC, when EPR squeezing values above 12 dB are considered.
Theory of resonance shifts of whispering gallery modes by arbitrary
plasmonic nanoparticles
Shifts of the resonance frequency of high Q whispering gallery modes (WGMs) in spherical dielectric microresonators by plasmonic nanoparticles can be greater than the WGM line width, such that the perturbation theory commonly used for describing resonance shifts by dielectric nanoparticles (Teraoka and Arnold 2006 J. Opt. Soc. Am. B 23 1381) is no longer applicable. This paper therefore reports on an analytic framework, based on generalized LorenzMie theory, capable of describing resonance shifts by metallic nanoparticles supporting plasmon oscillations. Generalization to nanoparticles of arbitrary geometry is presented by employing the extended boundary condition method. Within this framework, hybrid resonance conditions for coupled spherical photonic and plasmonic resonators are established and shown to simplify for small plasmonic nanoparticles. Approximate analytic formulae are derived for the shift and broadening of the isolated WGM and plasmon resonances, from which either apparent resonance shifts or mode splitting are shown to follow. Tuning of plasmon resonances using, for example, coreshell nanoparticles to attain a large spectral overlap between WGM and plasmon resonances is demonstrated to significantly enhance the magnitude of resonance shifts, with a 60fold enhancement achieved without any optimization. Hybridization of photonicplasmonic resonances is furthermore demonstrated (in addition to hybridization of transverse electrictransverse magnetic WGMs) and the associated level repulsion illustrated. Finally, the dependence of WGM resonance shifts on the orientation of silver nanorods is theoretically investigated and found to be strong by virtue of the asymmetry of the nanorod.
An azimuthally polarized light source for the optical near field
D. Ploss, A. Kriesch, H. Pfeifer, P. Banzer, U. Peschel
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Multipolar hierarchy of efficient quantum polarization measures
P. de la Hoz, A. B. Klimov, G. Bjork, Y. H. Kim, C. Mueller, Ch. Marquardt, G. Leuchs, L. L. SanchezSoto
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 higherorder polarization fluctuations.
GoosHanchen and ImbertFedorov beam shifts: an overview
We consider reflection and transmission of polarized paraxial light beams at a plane dielectric interface. The field transformations taking into account a finite beam width are described based on the planewave representation and geometric rotations. Using geometricaloptics coordinate frames accompanying the beams, we construct an effective Jones matrix characterizing spatialdispersion properties of the interface. This results in a unified selfconsistent description of the GoosHanchen and ImbertFedorov shifts (the latter being also known as the spin Hall effect of light). Our description reveals the intimate relation of the transverse ImbertFedorov shift to the geometric phases between constituent waves in the beam spectrum and to the angular momentum conservation for the whole beam. Both spatial and angular shifts are considered as well as their analogues for higherorder vortex beams carrying intrinsic orbital angular momentum. We also give a brief overview of various extensions and generalizations of the basic beamshift phenomena and related effects.
Pushing the limits of sensitivity and resolution in optical imaging
Siegfried Weisenburger, Marek Piliarik, Vahid Sandoghdar
ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY
246
(2013)
Low loss hollow opticalwaveguide connection from atmospheric pressure
to ultrahigh vacuum
A. Ermolov, K. F. Mak, F. Tani, P. Hoelzer, J. C. Travers, P. St J. Russell
A technique for optically accessing ultrahigh vacuum environments, via a photoniccrystal fiber with a long small hollow core, is described. The small core and the long bore enable a pressure ratio of over 10(8) to be maintained between two environments, while permitting efficient and unimpeded delivery of light, including ultrashort optical pulses. This delivery can be either passive or can encompass nonlinear optical processes such as optical pulse compression, deep UV generation, supercontinuum generation, or other useful phenomena. (C) 2013 AIP Publishing LLC.
Highly efficient coupling from an optical fiber to a nanoscale silicon
optomechanical cavity
Simon Groeblacher, Jeff T. Hill, Amir H. SafaviNaeini, Jasper Chan, Oskar Painter
We demonstrate highly efficient coupling of light from an optical fiber to a silicon photonic crystal optomechanical cavity. The fibertocavity coupling utilizes a compact ( L approximate to 25 mu m) intermediate adiabatic coupler. The optical coupling is lithographically controlled, broadband, relatively insensitive to fiber misalignment and allows for light to be transferred from an optical fiber to, in principle, any photonic chip with refractive index greater than that of the optical fiber. Here we demonstrate singlesided cavity coupling with a total fibertocavity optical power coupling efficiency of 85%. (c) 2013 AIP Publishing LLC.
Enhanced Raman Scattering of Graphene using Arrays of Split Ring
Resonators
George Sarau, Basudev Lahiri, Peter Banzer, Priti Gupta, Arnab Bhattacharya, Frank Vollmer, Silke Christiansen
Combining graphene with plasmonic nanostructures is currently being explored for high sensitivity biochemical detection based on the surfaceenhanced Raman scattering (SERS) effect. Here, a novel and tunable platform for understanding SERS based on graphene monolayers transferred on arrays of split ring resonators (SRRs) exhibiting resonances in the visible range is introduced. Raman enhancement factors per area of graphene of up to 75 are measured, demonstrating the strong plasmonic coupling between graphene and the metamaterial resonances. Apart from the incident laser light, both the photoluminescence signal emitted by the SRRs and the Raman scattered light from graphene contribute to the excitation of distinct resonances, resulting in different SERS. This new perspective allows control of SERS in the case of graphene on plasmonic metamaterials or nanostructures and potentially paves the way towards an advanced SERS substrate that could lead to the detection of single molecules attached to graphene in future biochemical sensing devices.
Kinetic study of Hterminated silicon nanowires oxidation in very first
stages
Muhammad Y. Bashouti, Kasra Sardashti, Juergen Ristein, Silke Christiansen
Oxidation of silicon nanowires (Si NWs) is an undesirable phenomenon that has a detrimental effect on their electronic properties. To prevent oxidation of Si NWs, a deeper understanding of the oxidation reaction kinetics is necessary. In the current work, we study the oxidation kinetics of hydrogenterminated Si NWs (HSi NWs) as the starting surfaces for molecular functionalization of Si surfaces. HSi NWs of 85nm average diameter were annealed at various temperatures from 50A degrees C to 400A degrees C, in shorttime spans ranging from 5 to 60 min. At high temperatures (T a parts per thousand yen 200A degrees C), oxidation was found to be dominated by the oxide growth site formation (made up of silicon suboxides) and subsequent silicon oxide selflimitation. SiSi backbond oxidation and SiH surface bond propagation dominated the process at lower temperatures (T < 200 degrees C).
Efficient optical pumping and high optical depth in a hollowcore
photoniccrystal fibre for a broadband quantum memory
Michael R. Sprague, Duncan G. England, Amir Abdolvand, Joshua Nunn, XianMin Jin, W. Steven Kolthammer, Marco Barbieri, Bruno Rigal, Patrick S. Michelberger, Tessa F. M. Champion, et al.
The generation of large multiphoton quantum statesfor applications in computing, metrology and simulationrequires a network of highefficiency quantum memories capable of storing broadband pulses. Integrating these memories into a fibre offers a number of advantages towards realizing this goal: strong lightmatter coupling at low powers, simplified alignment and compatibility with existing photonic architectures. Here, we introduce a largecore kagomestructured hollowcore fibre as a suitable platform for an integrated fibrebased quantum memory with a warm atomic vapour. We demonstrate, for the first time, efficient optical pumping in such a system, where 90 +/ 1% of atoms are prepared in the ground state. We measure high optical depths (3 x 10(4)) and narrow homogeneous linewidths (6 +/ 2 MHz) that do not exhibit significant transittime broadening, showing that we can prepare a Lambdalevel system in a pure state. Our results establish that kagome fibres are suitable for implementing a broadband, roomtemperature quantum memory, as well as a range of nonlinear optical effects.
Theory of optical activity in twisted photonic crystal fibers
T. Weiss, X. M. Xi, G. K. L. Wong, F. Biancalana, S. M. Barnett, M. J. Padgett, P. St. J. Russell
2013 CONFERENCE ON AND INTERNATIONAL QUANTUM ELECTRONICS CONFERENCE
LASERS AND ELECTROOPTICS EUROPE (CLEO EUROPE/IQEC)
(2013)
Controlling morphology and optical properties of selfcatalyzed,
maskfree GaN rods and nanorods by metalorganic vapor phase epitaxy
C. Tessarek, M. Bashouti, M. Heilmann, C. Dieker, I. Knoke, E. Spiecker, S. Christiansen
JOURNAL OF APPLIED PHYSICS
114(14)
144304
(2013)

Journal
A simple selfcatalyzed and maskfree approach will be presented to grow GaN rods and nanorods based on the metalorganic vapor phase epitaxy technique. The growth parameter dependent adjustment of the morphology of the structures will be discussed. Rods and nanorods with diameters reaching from a few mu m down to 100 nm, heights up to 48 mu m, and densities up to 8.10(7) cm(2) are all vertically aligned with respect to the sample surface and exhibiting a hexagonal shape with smooth sidewall facets. Optical properties of GaN nanorods were determined using cathodoluminescence. It will be shown that the optical properties can be improved just by reducing the Ga precursor flow. Furthermore, for regular hexagonal shaped rods and nanorods, whispering gallery modes with quality factors up to 500 were observed by cathodoluminescence pointing out high morphological quality of the structures. Structural investigations using transmission electron microscopy show that larger GaN nanorods (diameter > 500 nm) contain threading dislocations in the bottom part and vertical inversion domain boundaries, which separate a Gapolar core from a Npolar shell. In contrast, small GaN nanorods (similar to 200 nm) are largely free of such extended defects. Finally, evidence for a selfcatalyzed, Gainduced vaporliquidsolid growth will be discussed. (C) 2013 AIP Publishing LLC.
Efficient coupling to an optical resonator by exploiting timereversal
symmetry
M. Bader, S. Heugel, A. L. Chekhov, M. Sondermann, G. Leuchs
The interaction of a cavity with an external field is symmetric under time reversal. Thus, coupling to a resonator is most efficient when the incident light is the time reversed version of a free cavity decay, i.e. when it has a rising exponential shape matching the cavity lifetime. For light entering the cavity from only one side, the maximally achievable coupling efficiency is limited by the choice of the cavity mirrors' reflectivities. Such an emptycavity experiment serves also as a model system for singlephoton singleatom absorption dynamics. We present experiments coupling exponentially rising pulses to a cavity system which allows for high coupling efficiencies. The influence of the time constant of the rising exponential is investigated as well as the effect of a finite pulse duration. We demonstrate coupling 94% of the incident TEM00 mode into the resonator.
Gaintunable optomechanical cooling in a laser cavity
Li Ge, Sanli Faez, Florian Marquardt, Hakan E. Tuereci
Physical Review A
87(5)
053839
(2013)

Journal

PDF
We study the optical cooling of the cavity mirror in an active laser cavity. We find that the optical damping rate is vanishingly small for an incoherently pumped laser above threshold. In the presence of an additional external coherent drive however, the optical damping rate can be enhanced substantially with respect to that of a passive cavity. We show that the strength of the incoherent pump provides the means to tune the optical damping rate and the steady state phonon number. The system is found to undergo a transition from the weak optomechanical coupling regime to the strong optomechanical coupling regime as the strength of the incoherent pump is varied.
Creation and dynamics of remote spinentangled pairs in the expansion of
strongly correlated fermions in an optical lattice
Stefan Kessler, Ian P. McCulloch, Florian Marquardt
New Journal of Physics
15
053043
(2013)

Journal

PDF
We consider the nonequilibrium dynamics of an interacting spin1/2 fermion gas in a onedimensional optical lattice after switching off the confining potential. In particular, we study the creation and the time evolution of spatially separated, spinentangled fermionic pairs. The timedependent densitymatrix renormalization group is used to simulate the time evolution and evaluate the twosite spin correlation functions, from which the concurrence is calculated. We find that the typical distance between entangled fermions depends crucially on the onsite interaction strength, and that a timedependent modulation of the tunnelling amplitude can enhance the production of spin entanglement. Moreover, we discuss the prospects of experimentally observing these phenomena using spindependent singlesite detection.
Quantum ManyBody Dynamics in Optomechanical Arrays
Max Ludwig, Florian Marquardt
Physical Review Letters
111(7)
073603
(2013)

Journal

PDF
We study the nonlinear driven dissipative quantum dynamics of an array of optomechanical systems. At each site of such an array, a localized mechanical mode interacts with a laserdriven cavity mode via radiation pressure, and both photons and phonons can hop between neighboring sites. The competition between coherent interaction and dissipation gives rise to a rich phase diagram characterizing the optical and mechanical manybody states. For weak intercellular coupling, the mechanical motion at different sites is incoherent due to the influence of quantum noise. When increasing the coupling strength, however, we observe a transition towards a regime of phasecoherent mechanical oscillations. We employ a Gutzwiller ansatz as well as semiclassical Langevin equations on finite lattices, and we propose a realistic experimental implementation in optomechanical crystals.
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