Nanotextured surfaces provide an ideal platform for efficiently capturing and emitting light. However, the increased surface area in combination with surface defects induced by nanostructuring e.g. using reactive ion etching (RIE) negatively affects the device's active region and, thus, drastically decreases device performance. In this work, the influence of structural defects and surface states on the optical and electrical performance of InGaN/GaN nanorod (NR) light emitting diodes (LEDs) fabricated by top-down RIE of c-plane GaN with InGaN quantum wells was investigated. After proper surface treatment a significantly improved device performance could be shown. Therefore, wet chemical removal of damaged material in KOH solution followed by atomic layer deposition of only 10 nm alumina as wide bandgap oxide for passivation were successfully applied. Raman spectroscopy revealed that the initially compressively strained InGaN/GaN LED layer stack turned into a virtually completely relaxed GaN and partially relaxed InGaN combination after RIE etching of NRs. Time-correlated single photon counting provides evidence that both treatments-chemical etching and alumina deposition-reduce the number of pathways for non-radiative recombination. Steady-state photoluminescence revealed that the luminescent performance of the NR LEDs is increased by about 50% after KOH and 80% after additional alumina passivation. Finally, complete NR LED devices with a suspended graphene contact were fabricated, for which the effectiveness of the alumina passivation was successfully demonstrated by electroluminescence measurements.
New self-dual additive F4-codes constructed from circulant graphs
In order to construct quantum [[n,0,d]] codes for (n,d)=(56,15), (57,15), (58,16), (63,16), (67,17), (70,18), (71,18), (79,19), (83,20), (87,20), (89,21), (95,20), we construct self-dual additive F4-codes of length n and minimum weight d from circulant graphs. The quantum codes with these parameters are constructed for the first time.
Autonomous absolute calibration of an ICCD camera in single-photon
detection regime
Luo Qi,
Felix Just,
Gerd Leuchs,
Maria V. Chekhova
Optics Express
24
26444-26453
(2016)
| Journal
| PDF
Intensified charge coupled device (ICCD) cameras are widely used in vari-ous applications such as microscopy, astronomy, spectroscopy. Often they are used as single-photon detectors, with thresholding being an essential part of the readout. In this paper, we measure the quantum efficiency of an ICCD camera in the single-photon de-tection mode using the Klyshko absolute calibration technique. The quantum efficiency is obtained as a function of the threshold value and of the wavelength of the detected light. In addition, we study the homogeneity of the photon sensitivity over the camera chip area. The experiment is performed in the autonomous regime, without using any additional detectors. We therefore demonstrate the self-calibration of an ICCD camera.
Engineering the Frequency Spectrum of Bright Squeezed Vacuum via Group
Velocity Dispersion in an SU(1,1) Interferometer
Samuel Lemieux,
Mathieu Manceau,
Polina R. Sharapova,
Olga V. Tikhonova,
Robert W. Boyd,
Gerd Leuchs,
Maria V. Chekhova
Bright squeezed vacuum, a promising tool for quantum information, can be generated by high-gain parametric down-conversion. However, its frequency and angular spectra are typically quite broad, which is undesirable for applications requiring single-mode radiation. We tailor the frequency spectrum of high-gain parametric down-conversion using an SU(1,1) interferometer consisting of two nonlinear crystals with a dispersive medium separating them. The dispersive medium allows us to select a narrow band of the frequency spectrum to be exponentially amplified by high-gain parametric amplification. The frequency spectrum is thereby narrowed from (56.5±0.1) to (1.22±0.02) THz and, in doing so, the number of frequency modes is reduced from approximately 50 to 1.82±0.02. Moreover, this method provides control and flexibility over the spectrum of the generated light through the timing of the pump.
Single-shot reconstruction of spectral amplitude and phase in a fiber ring cavity at a 80 MHz repetition rate
Jonas Hammer,
Pooria Hosseini,
Curtis R. Menyuk,
Philip St. J. Russell,
Nicolas Y. Joly
Femtosecond pulses circulating in a synchronously driven fiber ring cavity have complex amplitude and phase profiles that can change completely from one round-trip to the next. We use a recently developed technique, combining dispersive Fourier transformation) with spectral interferometry, to reconstruct the spectral amplitude and phase at each round-trip and, thereby, follow in detail the pulse reorganization that occurs. We focus on two different regimes: a period-two regime in which the pulse alternates between two distinct states and a highly complex regime. We characterize the spectral amplitude and phase of the pulses in both regimes at a repetition rate of 75.6 MHz and find good agreement with modeling of the system based on numerical solutions of the generalized nonlinear Schrodinger equation with feedback. (C) 2016 Optical Society of America
Hybrid photonic-crystal fiber for single-mode phase matched generation of third harmonic and photon triplets
Andrea Cavanna,
Felix Just,
Xin Jiang,
Gerd Leuchs,
Maria V. Chekhova,
Philip St. J. Russell,
Nicolas Y. Joly
All-fiber systems for third harmonic generation are of great interest because they can be used for the inverse process, namely, the generation of entangled photon triplets. Usually, chromatic dispersion prevents phase matching between the incident and generated radiation when they are both guided in an LP01-like mode. Here, we present a hybrid photonic crystal fiber that has been designed for phase matched third harmonic generation from 1596 to 532 nm in single-lobed modes. The third harmonic radiation is guided by an all-solid bandgap microstructure, while the pump frequency is confined by conventional total internal reflection. The fiber is also suitable for the generation of photon triplet states.
Nonlinear interferometers in quantum optics
M. V. Chekhova,
Z. Y. Ou
Advances in Optics and Photonics
8
104-155
(2016)
| Journal
We review the main works in the field of nonlinear interferometers, which has been developing ever since the start of nonlinear optics and has seen growing interest in recent years due to the applications in quantum information and quantum metrology. Because the class of schemes that are referred to as nonlinear interferometers is too broad, we restrict the consideration to the cases in which crystals, fibers, or atomic systems producing the nonlinear effect are placed inside the interferometer, and only linear phase shifts are imposed. As a nonlinear effect, we consider four-wave mixing and parametric down-conversion, at both low and high gain.
Compartmentalization and Transport in Synthetic Vesicles
Christine Schmitt,
Anna H. Lippert,
Navid Bonakdar,
Vahid Sandoghdar,
Lars M. Voll
Frontiers in Bioengineering and Biotechnology
4
19
(2016)
| Journal
Nanoscale vesicles have become a popular tool in life sciences. Besides liposomes that are generated from phospholipids of natural origin, polymersomes fabricated of synthetic block copolymers enjoy increasing popularity, as they represent more versatile membrane building blocks that can be selected based on their specific physicochemical properties, such as permeability, stability, or chemical reactivity. In this review, we focus on the application of simple and nested artificial vesicles in synthetic biology. First, we provide an introduction into the utilization of multicompartmented vesosomes as compartmentalized nanoscale bioreactors. In the bottom-up development of protocells from vesicular nanoreactors, the specific exchange of pathway intermediates across compartment boundaries represents a bottleneck for future studies. To date, most compartmented bioreactors rely on unspecific exchange of substrates and products. This is either based on changes in permeability of the coblock polymer shell by physicochemical triggers or by the incorporation of unspecific porin proteins into the vesicle membrane. Since the incorporation of membrane transport proteins into simple and nested artificial vesicles offers the potential for specific exchange of substances between subcompartments, it opens new vistas in the design of protocells. Therefore, we devote the main part of the review to summarize the technical advances in the use of phospholipids and block copolymers for the reconstitution of membrane proteins.
Voices of biotech
Ido Amit,
David Baker,
Roger Barker,
Bonnie Berger,
Carolyn Bertozzi,
Sangeeta Bhatia,
Alessandra Biffi,
Francesca Demichelis,
Jennifer Doudna, et al.
Systematic Surface Phase Transition of Ag Thin Films by Iodine
Functionalization at Room Temperature: Evolution of Optoelectronic and
Texture Properties
Muhammad Y. Bashouti,
Razieh Talebi,
Thaer Kassar,
Arashmid Nahal,
Juergen Ristein,
Tobias Unruh,
Silke H. Christiansen
We show a simple room temperature surface functionalization approach using iodine vapour to control a surface phase transition from cubic silver (Ag) of thin films into wurtzite silver-iodid (beta-AgI) films. A combination of surface characterization techniques (optical, electronical and structural characterization) reveal distinct physical properties of the new surface phase. We discuss the AgI thin film formation dynamics and related transformation of physical properties by determining the work-function, dielectric constant and pyroelectric behavior together with morphological and structural thin film properties such as layer thickness, grain structure and texture formation. Notable results are: (i) a remarkable increase of the work-function (by 0.9 eV) of the Ag thin layer after short a iodine exposure time (<= 60 s), with simultaneous increase of the thin film transparency (by two orders of magnitude), (ii) pinning of the Fermi level at the valance band maximum upon iodine functionalization, (iii) 84% of all crystallites grain were aligned as a result of the evolution of an internal electric field. Realizing a nanoscale layer stack composed of a dielectric AgI layer on top of a metallic thin Ag layer with such a simple method has some technological implications e.g. to realize optical elements such as planar optical waveguides.
Unveiling the optical properties of a metamaterial synthesized by
electron-beam-induced deposition
P. Wozniak,
K. Hoeflich,
G. Broenstrup,
P. Banzer,
S. Christiansen,
G. Leuchs
Direct writing using a focused electron beam allows for fabricating truly three-dimensional structures of sub-wavelength dimensions in the visible spectral regime. The resulting sophisticated geometries are perfectly suited for studying light-matter interaction at the nanoscale. Their overall optical response will strongly depend not only on geometry but also on the optical properties of the deposited material. In the case of the typically used metal-organic precursors, the deposits show a substructure of metallic nanocrystals embedded in a carbonaceous matrix. Since gold-containing precursor media are especially interesting for optical applications, we experimentally determine the effective permittivity of such an effective material. Our experiment is based on spectroscopic measurements of planar deposits. The retrieved permittivity shows a systematic dependence on the gold particle density and cannot be sufficiently described using the common Maxwell-Garnett approach for effective medium.
Extended hot carrier lifetimes observed in bulk In0.265 +/- 0.02Ga0.735N
under high-density photoexcitation
Yi Zhang,
Murad J. Y. Tayebjee,
Suntrana Smyth,
Miroslav Dvorak,
Wen Xiaoming,
Xia Hongze,
Martin Heilmann,
Liao Yuanxun,
Zhang Zewen, et al.
We have investigated the ultrafast carrier dynamics in a 1 mu m bulk In0.265Ga0.735N thin film grown using energetic neutral atom-beam lithography/epitaxy molecular beam epitaxy. Cathodoluminescence and X-ray diffraction experiments are used to observe the existence of indium-rich domains in the sample. These domains give rise to a second carrier population and biexponential carrier cooling is observed with characteristic lifetimes of 1.6 and 14 ps at a carrier density of 1.3 x 10 16 cm(-3). A combination of band-filling, screening, and hot-phonon effects gives rise to a two-fold enhanced mono-exponential cooling rate of 28 ps at a carrier density of 8.4 x 10(18) cm(-3). This is the longest carrier thermalization time observed in bulk InGaN alloys to date. (C) 2016 AIP Publishing LLC.
High-resolution wavefront shaping with a photonic crystal fiber for
multimode fiber imaging
Lyubov V. Amitonova,
Adrien Descloux,
Joerg Petschulat,
Michael H. Frosz,
Goran Ahmed,
Fehim Babic,
Xin Jiang,
Allard P. Mosk,
Philip St. J. Russell, et al.
We demonstrate that a high-numerical-aperture photonic crystal fiber allows lensless focusing at an unparalleled resolution by complex wavefront shaping. This paves the way toward high-resolution imaging exceeding the capabilities of imaging with multi-core single-mode optical fibers. We analyze the beam waist and power in the focal spot on the fiber output using different types of fibers and different wavefront shaping approaches. We show that the complex wavefront shaping technique, together with a properly designed multimode photonic crystal fiber, enables us to create a tightly focused spot on the desired position on the fiber output facet with a subwavelength beam waist. (C) 2016 Optical Society of America
Near-ionization-threshold emission in atomic gases driven by intense
sub-cycle pulses
Wei-Chun Chu,
John C. Travers,
Philip St J. Russell
We study theoretically the dipole radiation of a hydrogen atom driven by an intense sub-cycle pulse. The time-dependent Schrodinger equation for the system is solved by ab initio calculation to obtain the dipole response. Remarkably, a narrowband emission lasting longer than the driving pulse appears at a frequency just above the ionization threshold. An additional calculation using the strong field approximation also recovers this emission, which suggests that it corresponds to the oscillation of nearly bound electrons that behave similarly to Rydberg electrons. The predicted phenomenon is unique to ultrashort driving pulses but not specific to any particular atomic structure.
The duality principle in the presence of postselection
Jonathan Leach,
Eliot Bolduc,
Filippo M. Miatto,
Kevin Piche,
Gerd Leuchs,
Robert W. Boyd
The duality principle, a cornerstone of quantum mechanics, limits the coexistence of wave and particle behaviours of quantum systems. This limitation takes a quantitative form when applied to the visibility V of interference fringes and predictability P of paths within a two-alternative system, which are bound by the inequality V-2 + P-2 <= 1. However, if such a system is coupled to its environment, it becomes possible to obtain conditional measures of visibility and predictability, i.e. measures that are conditioned on the state of the environment. We show that in this case, the predictability and visibility values can lead to an apparent violation of the duality principle. We experimentally realize this apparent violation in a controlled manner by enforcing a fair-sampling-like loophole via postselection. This work highlights some of the subtleties that one can encounter while interpreting familiar quantities such as which-alternative information and visibility. While we concentrated on an extreme example, it is of utmost importance to realise that such subtleties might also be present in cases where the results are not obviously violating an algebraic bound, making them harder (but not any less crucial) to detect.
Spontaneous generation of singularities in paraxial optical fields
In nonrelativistic quantum mechanics, the spontaneous generation of singularities in smooth and finite wave functions is a well understood phenomenon also occurring for free particles. We use the familiar analogy between the two-dimensional Schrodinger equation and the optical paraxial wave equation to define a new class of square-integrable paraxial optical fields that develop a spatial singularity in the focal point of a weakly focusing thin lens. These fields are characterized by a single real parameter whose value determines the nature of the singularity. This novel field enhancement mechanism may stimulate fruitful research for diverse technological and scientific applications. (C) 2016 Optical Society of America
Silicon Nanowire Sensors Enable Diagnosis of Patients via Exhaled Breath
Nisreen Shehada,
John C. Cancilla,
Jose S. Torrecilla,
Enrique S. Pariente,
Gerald Broenstrup,
Silke Christiansen,
Douglas W. Johnson,
Marcis Leja,
Michael P. A. Davies, et al.
Two of the biggest challenges in medicine today are the need to detect diseases in a noninvasive manner and to differentiate between patients using a single diagnostic tool. The current study targets these two challenges by developing a molecularly modified silicon nanowire field effect transistor (SiNW FET) and showing its use in the detection and classification of many disease breathprints (lung cancer, gastric cancer, asthma, and chronic obstructive pulmonary disease). The fabricated SiNW FETs are characterized and optimized based on a training set that correlate their sensitivity and selectivity toward volatile organic compounds (VOCs) linked with the various disease breathprints. The best sensors obtained in the training set are then examined under real-world clinical conditions, using breath samples from 374 subjects. Analysis of the clinical samples show that the optimized SiNW FETs can detect and discriminate between almost all binary comparisons of the diseases under examination with >80% accuracy. Overall, this approach has the potential to support detection of many diseases in a direct harmless way, which can reassure patients and prevent numerous unpleasant investigations.
Barrier inhomogeneities limited current and 1/f noise transport in GaN
based nanoscale Schottky barrier diodes
Ashutosh Kumar,
M. Heilmann,
Michael Latzel,
Raman Kapoor,
Intu Sharma,
M. Goebelt,
Silke H. Christiansen,
Vikram Kumar,
Rajendra Singh
The electrical behaviour of Schottky barrier diodes realized on vertically standing individual GaN nanorods and array of nanorods is investigated. The Schottky diodes on individual nanorod show highest barrier height in comparison with large area diodes on nanorods array and epitaxial film which is in contrast with previously published work. The discrepancy between the electrical behaviour of nanoscale Schottky diodes and large area diodes is explained using cathodoluminescence measurements, surface potential analysis using Kelvin probe force microscopy and 1ow frequency noise measurements. The noise measurements on large area diodes on nanorods array and epitaxial film suggest the presence of barrier inhomogeneities at the metal/semiconductor interface which deviate the noise spectra from Lorentzian to 1/f type. These barrier inhomogeneities in large area diodes resulted in reduced barrier height whereas due to the limited role of barrier inhomogeneities in individual nanorod based Schottky diode, a higher barrier height is obtained.
Unveiling the Hybrid n-Si/PEDOT:PSS Interface
Sara Jaeckle,
Martin Liebhaber,
Jens Niederhausen,
Matthias Buechele,
Roberto Felix,
Regan G. Wilks,
Marcus Baer,
Klaus Lips,
Silke Christiansen
We investigated the buried interface between monocrystalline n-type silicon (n-Si) and the highly conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), which is successfully applied as a hole selective contact in hybrid solar cells. We show that a post-treatment of the polymer films by immersion in a suitable solvent reduces the layer thickness by removal of excess material. We prove that this post-treatment does not affect the functionality of the hybrid solar cells. Through the thin layer we are probing the chemical structure at the n-Si/PEDOT:PSS interface with synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). From the HAXPES data we conclude that the Si substrate of a freshly prepared hybrid solar cell is already oxidized immediately after preparation. Moreover, we show that even when storing the sample in inert gas such as, e.g., nitrogen the n-Si/SiOx/PEDOT:PSS interface continues to further oxidize. Thus, without further surface treatment, an unstable Si suboxide will always be present at the hybrid interface.
Single-mode squeezing in arbitrary spatial modes
Marion Semmler,
Stefan Berg-Johansen,
Vanessa Chille,
Christian Gabriel,
Peter Banzer,
Andrea Aiello,
Christoph Marquardt,
Gerd Leuchs
As the generation of squeezed states of light has become a standard technique in laboratories, attention is increasingly directed towards adapting the optical parameters of squeezed beams to the specific requirements of individual applications. It is known that imaging, metrology, and quantum information may benefit from using squeezed light with a tailored transverse spatial mode. However, experiments have so far been limited to generating only a few squeezed spatial modes within a given setup. Here, we present the generation of single-mode squeezing in Laguerre-Gauss and Bessel-Gauss modes, as well as an arbitrary intensity pattern, all from a single setup using a spatial light modulator (SLM). The degree of squeezing obtained is limited mainly by the initial squeezing and diffractive losses introduced by the SLM, while no excess noise from the SLM is detectable at the measured sideband. The experiment illustrates the single-mode concept in quantum optics and demonstrates the viability of current SLMs as flexible tools for the spatial reshaping of squeezed light. (C) 2016 Optical Society of America
Coherent octave-spanning mid-infrared supercontinuum generated in
As2S3-silica double-nanospike waveguide pumped by femtosecond Cr:ZnS
laser
Shangran Xie,
Nikolai Tolstik,
John C. Travers,
Evgeni Sorokin,
Celine Caillaud,
Johann Troles,
Philip St J. Russell,
Irina T. Sorokina
A more than 1.5 octave-spanning mid-infrared supercontinuum (1.2 to 3.6 mu m) is generated by pumping a As2S3-silica "double-nanospike" waveguide via a femtosecond Cr:ZnS laser at 2.35 mu m. The combination of the optimized group velocity dispersion and extremely high nonlinearity provided by the As2S3-silica hybrid waveguide enables a similar to 100 pJ level pump pulse energy threshold for octave-spanning spectral broadening at a repetition rate of 90 MHz. Numerical simulations show that the generated supercontinuum is highly coherent over the entire spanning wavelength range. The results are important for realization of a high repetition rate octave-spanning frequency comb in the mid-infrared spectral region. (C)2016 Optical Society of America
Experimental generation of amplitude squeezed vector beams
Vanessa Chille,
Stefan Berg-Johansen,
Marion Semmler,
Peter Banzer,
Andrea Aiello,
Gerd Leuchs,
Christoph Marquardt
We present an experimental method for the generation of amplitude squeezed high-order vector beams. The light is modified twice by a spatial light modulator such that the vector beam is created by means of a collinear interferometric technique. A major advantage of this approach is that it avoids systematic losses, which are detrimental as they cause decoherence in continuous-variable quantum systems. The utilisation of a spatial light modulator (SLM) gives the flexibility to switch between arbitrary mode orders. The conversion efficiency with our setup is only limited by the efficiency of the SLM. We show the experimental generation of Laguerre-Gauss (LG) modes with radial indices 0 or 1 and azimuthal indices up to 3 with complex polarization structures and a quantum noise reduction up to -0.9dB +/- 0.1dB. The corresponding polarization structures are studied in detail by measuring the spatial distribution of the Stokes parameters. (C) 2016 Optical Society of America
Optical Polarization Mobius Strips and Points of Purely Transverse Spin
Density
Thomas Bauer,
Martin Neugebauer,
Gerd Leuchs,
Peter Banzer
Tightly focused light beams can exhibit complex and versatile structured electric field distributions. The local field may spin around any axis including a transverse axis perpendicular to the beams' propagation direction. At certain focal positions, the corresponding local polarization ellipse can even degenerate into a perfect circle, representing a point of circular polarization or C point. We consider the most fundamental case of a linearly polarized Gaussian beam, where-upon tight focusing-those C points created by transversely spinning fields can form the center of 3D optical polarization topologies when choosing the plane of observation appropriately. Because of the high symmetry of the focal field, these polarization topologies exhibit nontrivial structures similar to Mobius strips. We use a direct physical measure to find C points with an arbitrarily oriented spinning axis of the electric field and experimentally investigate the fully three-dimensional polarization topologies surrounding these C points by exploiting an amplitude and phase reconstruction technique.
Influence of the substrate material on the knife-edge based profiling of
tightly focused light beams
The performance of the knife-edge method as a beam profiling technique for tightly focused light beams depends on several parameters, such as the material and height of the knife-pad as well as the polarization and wavelength of the focused light beam under study. Here we demonstrate that the choice of the substrate the knife-pads are fabricated on has a crucial influence on the reconstructed beam projections as well. We employ an analytical model for the interaction of the knife-pad with the beam and report good agreement between our numerical and experimental results. Moreover, we simplify the analytical model and demonstrate, in which way the underlying physical effects lead to the apparent polarization dependent beam shifts and changes of the beamwidth for different substrate materials and heights of the knife-pad. (C) 2016 Optical Society of America
Fluorescence-based remote irradiation sensor in liquid-filled
hollow-core photonic crystal fiber
R. Zeltner,
D. S. Bykov,
S. Xie,
T. G. Euser,
P. St. J. Russell
We report an irradiation sensor based on a fluorescent "flying particle" that is optically trapped and propelled inside the core of a water-filled hollow-core photonic crystal fiber. When the moving particle passes through an irradiated region, its emitted fluorescence is captured by guided modes of the fiber core and so can be monitored using a filtered photodiode placed at the fiber end. The particle speed and position can be precisely monitored using in-fiber Doppler velocimetry, allowing the irradiation profile to be measured to a spatial resolution of similar to 10 mu m. The spectral response can be readily adjusted by appropriate choice of particle material. Using dye-doped polystyrene particles, we demonstrate detection of green (532 nm) and ultraviolet (340 nm) light. Published by AIP Publishing.
Attacks on practical quantum key distribution systems (and how to
prevent them)
Nitin Jain,
Birgit Stiller,
Imran Khan,
Dominique Elser,
Christoph Marquardt,
Gerd Leuchs
With the emergence of an information society, the idea of protecting sensitive data is steadily gaining importance. Conventional encryption methods may not be sufficient to guarantee data protection in the future. Quantum key distribution (QKD) is an emerging technology that exploits fundamental physical properties to guarantee perfect security in theory. However, it is not easy to ensure in practice that the implementations of QKD systems are exactly in line with the theoretical specifications. Such theory-practice deviations can open loopholes and compromise security. Several such loopholes have been discovered and investigated in the last decade. These activities have motivated the proposal and implementation of appropriate countermeasures, thereby preventing future attacks and enhancing the practical security of QKD. This article introduces the so-called field of quantum hacking by summarising a variety of attacks and their prevention mechanisms.
Spatially-controlled laser-induced decoration of 2D and 3D substrates
with plasmonic nanoparticles
M. Y. Bashouti,
A. V. Povolotckaia,
A. V. Povolotskiy,
S. P. Tunik,
S. H. Christiansen,
G. Leuchs,
A. A. Manshina
We demonstrate a new approach which can be used for targeted imparting of plasmonic properties for a wide range of different substrates (transparent and non-transparent) which may have any 2D or 3D topological structure created independently in a prior step with some other technology.
Towards Laser-based Photonic Chip Integrated Quantum Random Number
Generators
M. Sabuncu
LASERS IN ENGINEERING
33
(1-3)
117-127
(2016)
Lasers are recently being used more frequently in random number generators. The world record in random number generation was broken by the help of lasers. The world's fastest quantum random number generators utilize lasers to tap into the random fluctuations in order to extract true random bit sequences. We investigate a system based on a Nd:YAG laser that potentially generates true random bits at Gbit/s rates. As photonic on chip technologies progress we foresee laser based high speed random number generators integrated on chips. Such a photonic chip will create a revolution in the technology of security devices that employ quantum cryptography techniques for secure communication.
Quantum Nondemolition Measurement of a Quantum Squeezed State Beyond the
3 dB Limit
C. U. Lei,
A. J. Weinstein,
J. Suh,
E. E. Wollman,
A. Kronwald,
F. Marquardt,
A. A. Clerk,
K. C. Schwab
We use a reservoir engineering technique based on two-tone driving to generate and stabilize a quantum squeezed state of a micron-scale mechanical oscillator in a microwave optomechanical system. Using an independent backaction-evading measurement to directly quantify the squeezing, we observe 4.7±0.9 dB of squeezing below the zero-point level surpassing the 3 dB limit of standard parametric squeezing techniques. Our measurements also reveal evidence for an additional mechanical parametric effect. The interplay between this effect and the optomechanical interaction enhances the amount of squeezing obtained in the experiment.
Entanglement rate for Gaussian continuous variable beams
Zhi Jiao Deng,
Steven J. M. Habraken,
Florian Marquardt
New Journal of Physics
18
063022
(2016)
| Journal
| PDF
We derive a general expression that quantifies the total entanglement production rate in continuous variable systems, where a source emits two entangled Gaussian beams with arbitrary correlators. This expression is especially useful for situations where the source emits an arbitrary frequency spectrum, e.g. when cavities are involved. To exemplify its meaning and potential, we apply it to a four-mode optomechanical setup that enables the simultaneous up- and down-conversion of photons from a drive laser into entangled photon pairs. This setup is efficient in that both the drive and the optomechanical up- and down-conversion can be fully resonant.
Classical dynamical gauge fields in optomechanics
Stefan Walter,
Florian Marquardt
New Journal of Physics
18
113029
(2016)
| Journal
| PDF
Artificial gauge fields for neutral particles such as photons, recently attracted a lot of attention in various fields ranging from photonic crystals to ultracold atoms in optical lattices to optomechanical arrays. Here we point out that, among all implementations of gauge fields, the optomechanical setting allows for the most natural extension where the gauge field becomes dynamical. The mechanical oscillation phases determine the effective artificial magnetic field for the photons, and once these phases are allowed to evolve, they respond to the flow of photons in the structure. We discuss a simple three-site model where we identify four different regimes of the gauge-field dynamics. Furthermore, we extend the discussion to a two-dimensional lattice. Our proposed scheme could for instance be implemented using optomechanical crystals.
Coupled spin-light dynamics in cavity optomagnonics
Silvia Viola-Kusminskiy,
Hong X. Tang,
Florian Marquardt
Physical Review A
94
(3)
033821
(2016)
| Journal
| PDF
Experiments during the past 2 years have shown strong resonant photon-magnon coupling in microwave cavities, while coupling in the optical regime was demonstrated very recently for the first time. Unlike with microwaves, the coupling in optical cavities is parametric, akin to optomechanical systems. This line of research promises to evolve into a new field of optomagnonics, aimed at the coherent manipulation of elementary magnetic excitations in solid-state systems by optical means. In this work we derive the microscopic optomagnonic Hamiltonian. In the linear regime the system reduces to the well-known optomechanical case, with remarkably large coupling. Going beyond that, we study the optically induced nonlinear classical dynamics of a macrospin. In the fast-cavity regime we obtain an effective equation of motion for the spin and show that the light field induces a dissipative term reminiscent of Gilbert damping. The induced dissipation coefficient, however, can change sign on the Bloch sphere, giving rise to self-sustained oscillations. When the full dynamics of the system is considered, the system can enter a chaotic regime by successive period doubling of the oscillations.
Topological Quantum Fluctuations and Traveling Wave Amplifiers
Vittorio Peano,
Martin Houde,
Florian Marquardt,
Aashish A. Clerk
Physical Review X
6
(4)
041026
(2016)
| Journal
| PDF
It is now well established that photonic systems can exhibit topological energy bands. Similar to their electronic counterparts, this leads to the formation of chiral edge modes which can be used to transmit light in a manner that is protected against backscattering. While it is understood how classical signals can propagate under these conditions, it is an outstanding important question how the quantum vacuum fluctuations of the electromagnetic field get modified in the presence of a topological band structure. We address this challenge by exploring a setting where a nonzero topological invariant guarantees the presence of a parametrically unstable chiral edge mode in a system with boundaries, even though there are no bulk-mode instabilities. We show that one can exploit this to realize a topologically protected, quantum-limited traveling wave parametric amplifier. The device is naturally protected against both internal losses and backscattering; the latter feature is in stark contrast to standard traveling wave amplifiers. This adds a new example to the list of potential quantum devices that profit from topological transport.
New insights into colloidal gold flakes: structural investigation,
micro-ellipsometry and thinning procedure towards ultrathin
monocrystalline layers
B. Hoffmann,
M. Y. Bashouti,
T. Feichtner,
M. Mackovic,
C. Dieker,
A. M. Salaheldin,
P. Richter,
O. D. Gordan,
D. R. T. Zahn, et al.
High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, presumably single-crystalline gold flakes due to their superior materials properties. However, important details about their intrinsic structure and their optical properties are not well understood yet. In this study, we present a synthesis routine for large flakes with diameters of up to 70 mu m and an in-depth investigation of their structural and optical properties. The flakes are precisely analyzed by transmission electron microscopy, electron backscatter diffraction and micro-ellipsometry. We found new evidence for the existence of twins extending parallel to the Au flake {111} surfaces which have been found to not interfere with the presented nanopatterning. Micro-Ellipsometry was carried out to determine the complex dielectric function and to compare it to previous measurements of bulk single crystalline gold. Finally, we used focused ion beam milling to prepare smooth crystalline layers and high-quality nanostructures with desired thickness down to 10 nm to demonstrate the outstanding properties of the flakes. Our findings support the plasmonics and nano optics community with a better understanding of this material which is ideally suited for superior plasmonic nanostructures.
A miniaturized electron source based on dielectric laser accelerator
operation at higher spatial harmonics and a nanotip photoemitter
Joshua McNeur,
Martin Kozak,
Dominik Ehberger,
Norbert Schoenenberger,
Alexander Tafel,
Ang Li,
Peter Hommelhoff
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
49
(3)
034006
(2016)
| Journal
Here we propose a miniaturized electron source driven by recent experimental results of laser-triggered electron emission from tungsten nanotips and dielectric laser acceleration of sub relativistic electrons with velocities as low as 5.7 x 10(7)m s(-1) or energies as low as 9.6 keV, less than 20% of the speed of light. The recently observed laser-triggered emission of coherent low-emittance electron pulses from tungsten nanotips naturally lends itself towards incorporation with subrelativistic dielectric laser accelerators (DLAs). These structures have previously been shown to accelerate 28 keV electrons and here we report on the utilization of the 4th and 5th spatial harmonics of near fields in the single grating DLA to achieve acceleration of electrons with kinetic energies of 15.2 and 9.6 keV. We then propose the combination of needle tip emitters with subrelativistic accelerators to form a mm-scale device capable of producing electrons with arbitrary energies.
Measuring the modulus of the spatial coherence function using an error
tolerant phase shifting algorithm and a continuous lateral shearing
interferometer
Irina Harder,
Martin Eisner,
Reinhard Voelkel,
Sergej Rothau,
Johannes Schwider,
Peter Schwider
The modulus of the degree of coherence can be derived from interference patterns either by using fringes and next neighbour operations or by using several interferograms produced through phase shifting. Here the latter approach will be followed by using a lateral shearing interferometer exploiting a diffractive grating wedge providing a linearly progressive shear. Phase shifting methods offer pixel-oriented evaluations but suffer from instabilities and drifts which is the reason for the derivation of an error immune algorithm. This algorithm will use five pi/2-steps of the reference phase also for the calculation of the modulus of the coherence function. (C) 2016 Optical Society of America
Tunable optical parametric generator based on the pump spatial walk-off
Andrea Cavanna,
Felix Just,
Polina R. Sharapova,
Michael Taheri,
Gerd Leuchs,
Maria V. Chekhova
We suggest a novel optical parametric generator (OPG) in which one of the downconverted beams is spontaneously generated along the Poynting vector of the pump beam. In this configuration, the generation takes advantage of the walk-off of the extraordinary pump, rather than being degraded by it. As a result, the generated signal and idler beams are bright due to a high conversion efficiency, spatially nearly single mode due to the preferred direction of the Poynting vector, tunable over a wide range of wavelengths and broadband. The two beams are also correlated in frequency and in the photon number per pulse. Furthermore, due to their thermal statistics, these beams can be used as a pump to efficiently generate other nonlinear processes. (C) 2016 Optical Society of America
Demonstration of local teleportation using classical entanglement
Diego Guzman-Silva,
Robert Bruening,
Felix Zimmermann,
Christian Vetter,
Markus Graefe,
Matthias Heinrich,
Stefan Nolte,
Michael Duparre,
Andrea Aiello, et al.
Teleportation describes the transmission of information without transport of neither matter nor energy. For many years, however, it has been implicitly assumed that this scheme is of inherently nonlocal nature, and therefore exclusive to quantum systems. Here, we experimentally demonstrate that the concept of teleportation can be readily generalized beyond the quantum realm. We present an optical implementation of the teleportation protocol solely based on classical entanglement between spatial and modal degrees of freedom, entirely independent of nonlocality. Our findings could enable novel methods for distributing information between different transmission channels and may provide the means to leverage the advantages of both quantum and classical systems to create a robust hybrid communication infrastructure.
Coupling mechanical degrees of freedom with plasmonic resonances has potential applications in optomechanics, sensing, and active plasmonics. Here we demonstrate a suspended two-wire plasmonic nanoantenna acting like a nanoelectrometer. The antenna wires are supported and electrically connected via thin leads without disturbing the antenna resonance. As a voltage is applied, equal charges are induced on both antenna wires. The resulting equilibrium between the repulsive Coulomb force and the restoring elastic bending force enables us to precisely control the gap size. As a result the resonance wavelength and the field enhancement of the suspended optical nanoantenna can be reversibly tuned. Our experiments highlight the potential to realize large bandwidth optical nanoelectromechanical systems.
Resonant photo-ionization of Yb+ to Yb2+
Simon Heugel,
Martin Fischer,
Vladimir Elman,
Robert Maiwald,
Markus Sondermann,
Gerd Leuchs
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
49
(1)
015002
(2016)
| Journal
We demonstrate the controlled creation of a Yb-174(2+) ion by photo-ionizing Yb-174(+) with weak continuous-wave lasers at ultraviolet wavelengths. The photo-ionization is performed by resonantly exciting transitions of the Yb-174(+) ion in three steps. Starting from an ion crystal of two laser-cooled Yb-174(+) ions localized in a radio-frequency trap, the verification of the ionization process is performed by characterizing the properties of the resulting mixed-species ion-crystal. The obtained results facilitate fundamental studies of physics involving Yb2+ ions.
Guiding 2.94 mu m using low-loss microstructured antiresonant
triangular-core fibers
Yang Chen,
Mohammed F. Saleh,
Nicolas Y. Joly,
Fabio Biancalana
JOURNAL OF APPLIED PHYSICS
119
(14)
143104
(2016)
| Journal
We introduce a new simple design of hollow-core microstructured fiber targeted to guide mid-infrared light at a wavelength of 2.94 mu m. The fiber has a triangular-core supported via silica-glass webs enclosed by a large hollow capillary tube. The fiber specific dimensions are determined by the anti-resonant guiding mechanism. For a triangular-core with side length 100 mu m, the fiber has a minimum transmission loss 0.08 +/- 0.005 dB/m and dispersion 2.3 ps/km/nm at the operational wavelength of 2.94 mu m. (C) 2016 AIP Publishing LLC.
Self-Catalyzed Growth of Vertically Aligned InN Nanorods by
Metal-Organic Vapor Phase Epitaxy
C. Tessarek,
S. Fladischer,
C. Dieker,
G. Sarau,
B. Hoffmann,
M. Bashouti,
M. Goebelt,
M. Heilmann,
M. Latzel, et al.
Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal organic vapor phase epitaxy without any foreign catalyst. The In droplets on top of the nanorod's indicate a self-catalytic vapor liquid solid growth mode. A systematic study on important growth parameters has been carried out for the optimization of nanorod morphology. The nanorod N-polarity, induced by high temperature nitridation of the sapphire substrate, IS necessary to achieve vertical growth. Hydrogen, usually inapplicable during InN growth due to formation of metallic indium, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the sapphire surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temperature is similar. Transmission electron microscopy, spatially resolved energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been performed to analyze the structural properties. Spatially resolved cathodoluminescence investigations are carried out to verify the optical activity of the InN nanorods. The InN nanorods are expected to be the material of choice for high-efficiency hot carrier solar cells.
Vertically Oriented Growth of GaN Nanorods on Si Using Graphene as an
Atomically Thin Buffer Layer
Martin Heilmann,
A. Mazid Munshi,
George Sarau,
Manuela Goebelt,
Christian Tessarek,
Vidar T. Fauske,
Antonius T. J. van Helvoort,
Jianfeng Yang,
Michael Latzel, et al.
The monolithic integration,of wurtzite GaN on Si via metal organic vapor phase epitaxy is strongly hampered by lattice and thermal mismatch as well as meltback etching. This study presents single-layer graphene as an atomically thin buffer layer for c-axis-oriented growth of vertically aligned GaN nanorods mediated by nanometer-sized AlGaN nucleation islands. Nanostructures of, similar morphology are demonstrated on graphene-covered Si(111) as well as Si(100). High crystal and optical quality of the nanorods are evidenced through scanning transmission electron microscopy, micro-Raman, and cathodoluminescence measurements, supported by finite-difference time-domain simulations. Current voltage characteristics revealed high vertical conduction of the as-grown GaN nanorods through the Si substrates. These findings are substantial to advance the integration of GaN-based devices on any substrates of choice that sustains the GaN growth temperatures, thereby permitting novel designs of GaN-based heterojunction device concepts.
Efficient microwave to optical photon conversion: an electro-optical
realization
Alfredo Rueda,
Florian Sedlmeir,
Michele C. Collodo,
Ulrich Vogl,
Birgit Stiller,
Gerhard Schunk,
Dmitry V. Strekalov,
Christoph Marquardt,
Johannes M. Fink, et al.
Linking classical microwave electrical circuits to the optical telecommunication band is at the core of modern communication. Future quantum information networks will require coherent microwave-to-optical conversion to link electronic quantum processors and memories via low-loss optical telecommunication networks. Efficient conversion can be achieved with electro-optical modulators operating at the single microwave photon level. In the standard electro-optic modulation scheme, this is impossible because both up-and down-converted sidebands are necessarily present. Here, we demonstrate true single-sideband up-or down-conversion in a triply resonant whispering gallery mode resonator by explicitly addressing modes with asymmetric free spectral range. Compared to previous experiments, we show a 3 orders of magnitude improvement of the electro-optical conversion efficiency, reaching 0.1% photon number conversion for a 10 GHz microwave tone at 0.42 mW of optical pump power. The presented scheme is fully compatible with existing superconducting 3D circuit quantum electrodynamics technology and can be used for nonclassical state conversion and communication. Our conversion bandwidth is larger than 1 MHz and is not fundamentally limited. (C) 2016 Optical Society of America
Progress towards practical device-independent quantum key distribution
with spontaneous parametric down-conversion sources, on-off
photodetectors, and entanglement swapping
Kaushik P. Seshadreesan,
Masahiro Takeoka,
Masahide Sasaki
Device-independent quantum key distribution (DIQKD) guarantees unconditional security of a secret key without making assumptions about the internal workings of the devices used for distribution. It does so using the loophole-free violation of a Bell's inequality. The primary challenge in realizing DIQKD in practice is the detection loophole problem that is inherent to photonic tests of Bell' s inequalities over lossy channels. We revisit the proposal of Curty and Moroder [Phys.Rev.A 84, 010304(R) (2011)] to use a linear optics-based entanglement-swapping relay (ESR) to counter this problem. We consider realistic models for the entanglement sources and photodetectors: more precisely, (a) polarization-entangled states based on pulsed spontaneous parametric down-conversion sources with infinitely higher-order multiphoton components and multimode spectral structure, and (b) on-off photodetectors with nonunit efficiencies and nonzero dark-count probabilities. We show that the ESR-based scheme is robust against the above imperfections and enables positive key rates at distances much larger than what is possible otherwise.
Ring-shaped spectra of parametric downconversion and entangled photons
that never meet
Kirill Yu. Spasibko,
Denis A. Kopylov,
Tatiana V. Murzina,
Gerd Leuchs,
Maria V. Chekhova
We report on the observation of an unusual type of parametric downconversion. In the regime where collinear degenerate emission is in the anomalous range of group-velocity dispersion, its spectrum is restricted in both angle and wavelength. Detuning from exact collinear-degenerate phase-matching leads to a ring shape of the wavelength-angular spectrum, suggesting a new type of spatiotemporal coherence and entanglement of photon pairs. By imposing a phase varying in a specific way in both angle and wavelength, one can obtain an interesting state of an entangled photon pair, with the two photons being never at the same point at the same time. (C) 2016 Optical Society of America
Integrated plasmonic metasurfaces for spectropolarimetry
Wei Ting Chen,
Peter Torok,
Matthew R. Foreman,
Chun Yen Liao,
Wei-Yi Tsai,
Pei Ru Wu,
Din Ping Tsai
Plasmonic metasurfaces enable simultaneous control of the phase, momentum, amplitude and polarization of light and hence promise great utility in realization of compact photonic devices. In this paper, we demonstrate a novel chip-scale device suitable for simultaneous polarization and spectral measurements through use of six integrated plasmonic metasurfaces (IPMs), which diffract light with a given polarization state and spectral component into well-defined spatial domains. Full calibration and characterization of our device is presented, whereby good spectral resolution and polarization accuracy over a wavelength range of 500-700 nm is shown.
Functionality of our device in a Muller matrix modality is demonstrated through determination of the polarization properties of a commercially available variable waveplate. Our proposed IPM is robust, compact and can be fabricated with a single photolithography step, promising many applications in polarization imaging, quantum communication and quantitative sensing.
RF-dressed Rydberg atoms in hollow-core fibres
C. Veit,
G. Epple,
H. Kuebler,
T. G. Euser,
P. St J. Russell,
R. Loew
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
49
(13)
134005
(2016)
| Journal
The giant electro-optical response of Rydberg atoms manifests itself in the emergence of sidebands in the Rydberg excitation spectrum if the atom is exposed to a radio-frequency (RF) electric field. Here we report on the study of RF-dressed Rydberg atoms inside hollow-core photonic crystal fibres, a system that enables the use of low modulation voltages and offers the prospect of miniaturised vapour-based electro-optical devices. Narrow spectroscopic features caused by the RF field are observed for modulation frequencies up to 500 MHz.
30 years of squeezed light generation
Ulrik L. Andersen,
Tobias Gehring,
Christoph Marquardt,
Gerd Leuchs
Squeezed light generation has come of age. Significant advances on squeezed light generation have been made over the last 30 years-from the initial, conceptual experiment in 1985 till today's top-tuned, application-oriented setups. Here we review the main experimental platforms for generating quadrature squeezed light that have been investigated in the last 30 years.
Gold platelets for high-quality plasmonics A material with superior
nanostructuring properties
Inorganic photovoltaics - Planar and nanostructured devices
Jeyakumar Ramanujam,
Amit Verma,
B. Gonzalez-Diaz,
R. Guerrero-Lemus,
Carlos del Canizo,
Elisa Garcia-Tabares,
Ignacio Rey-Stolle,
Filip Granek,
Lars Korte, et al.
PROGRESS IN MATERIALS SCIENCE
82
294-404
(2016)
| Journal
Since its invention in the 1950s, semiconductor solar cell technology has evolved in great leaps and bounds. Solar power is now being considered as a serious leading contender for replacing fossil fuel based power generation. This article reviews the evolution and current state, and potential areas of near future research focus, of leading inorganic materials based solar cells, including bulk crystalline, amorphous thin-films, and nanomaterials based solar cells. Bulk crystalline silicon solar cells continue to dominate the solar power market, and continued efforts at device fabrication improvements, and device topology advancements are discussed. III-V compound semiconductor materials, on c-Si for solar power generation are also reviewed. Developments in thin-film based solar cells are reviewed, with a focus on amorphous silicon, copper zinc tin sulfide, cadmium telluride, as well as nanostructured cadmium telluride. Recent developments in the use of nano-materials for solar power generation, including silicon and gallium arsenide nanowires, are also reviewed. (C) 2016 Elsevier Ltd. All rights reserved.
Laser-driven acceleration of subrelativistic electrons near a
nanostructured dielectric grating: From acceleration via higher spatial
harmonics to necessary elements of a dielectric accelerator
Josh McNeur,
Martin Kozak,
Norbert Schoenenberger,
Ang Li,
Alexander Tafel,
Peter Hommelhoff
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS
SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
829
50-51
(2016)
| Journal
The experimental setup that allows for the observation of energy gain of electrons interacting with Dielectric Laser Accelerators (DLAs) is reviewed. Moreover, recent results, including acceleration due to electron interaction with third, fourth and fifth spatial harmonics of a nanostructured grating are discussed and an extended outlook is given. (C) 2016 Elsevier B.V. All rights reserved.
Transverse and longitudinal characterization of electron beams using
interaction with optical near-fields
Martin Kozak,
Joshua McNeur,
Kenneth J. Leedle,
Huiyang Deng,
Norbert Schoenenberger,
Axel Ruehl,
Ingmar Hartl,
Heinar Hoogland,
Ronald Holzwarth, et al.
We demonstrate an experimental technique for both transverse and longitudinal characterization of bunched femtosecond free electron beams. The operation principle is based on monitoring of the current of electrons that obtained an energy gain during the interaction with the synchronized optical near-field wave excited by femtosecond laser pulses. The synchronous accelerating/decelerating fields confined to the surface of a silicon nanostructure are characterized using a highly focused sub-relativistic electron beam. Here the transverse spatial resolution of 450 nm and femtosecond temporal resolution of 480 fs (sub-optical-cycle temporal regime is briefly discussed) achievable by this technique are demonstrated. (C) 2016 Optical Society of America
Integrating a DNA Strand Displacement Reaction with a Whispering Gallery
Mode Sensor for Label-Free Mercury (II) Ion Detection
Fengchi Wu,
Yuqiang Wu,
Zhongwei Niu,
Frank Vollmer
Mercury is an extremely toxic chemical pollutant of our environment. It has attracted the world's attention due to its high mobility and the ease with which it accumulates in organisms. Sensitive devices and methods specific for detecting mercury ions are, hence, in great need. Here, we have integrated a DNA strand displacement reaction with a whispering gallery mode (WGM) sensor for demonstrating the detection of Hg2+ ions. Our approach relies on the displacement of a DNA hairpin structure, which forms after the binding of mercury ions to an aptamer DNA sequence. The strand displacement reaction of the DNA aptamer provides highly specific and quantitative means for determining the mercury ion concentration on a label-free WGM sensor platform. Our approach also shows the possibility for manipulating the kinetics of a strand displacement reaction with specific ionic species.
Operational meaning of quantum measures of recovery
Tom Cooney,
Christoph Hirche,
Ciara Morgan,
Jonathan P. Olson,
Kaushik P. Seshadreesan,
John Watrous,
Mark M. Wilde
Several information measures have recently been defined that capture the notion of recoverability. In particular, the fidelity of recovery quantifies how well one can recover a system A of a tripartite quantum state, defined on systems ABC, by acting on system C alone. The relative entropy of recovery is an associated measure in which the fidelity is replaced by relative entropy. In this paper we provide concrete operational interpretations of the aforementioned recovery measures in terms of a computational decision problem and a hypothesis testing scenario. Specifically, we show that the fidelity of recovery is equal to the maximum probability with which a computationally unbounded quantum prover can convince a computationally bounded quantum verifier that a given quantum state is recoverable. The quantum interactive proof system giving this operational meaning requires four messages exchanged between the prover and verifier, but by forcing the prover to perform actions in superposition, we construct a different proof system that requires only two messages. The result is that the associated decision problem is in QIP(2) and another argument establishes it as hard for QSZK (both classes contain problems believed to be difficult to solve for a quantum computer). We finally prove that the regularized relative entropy of recovery is equal to the optimal type II error exponent when trying to distinguish many copies of a tripartite state from a recovered version of this state, such that the type I error is constrained to be no larger than a constant.
Lateral spin transport in paraxial beams of light
Martin Neugebauer,
Simon Grosche,
Sergej Rothau,
Gerd Leuchs,
Peter Banzer
We investigate the lateral transport of (longitudinal) spin angular momentum in a special polarization tailored light beam composed of a superposition of a y-polarized zero-order and an x-polarized first-order Hermite-Gaussian mode. This phenomenon is linked to the relative Gouy phase shift between the individual modes upon propagation, but can also be interpreted as a geometric phase effect. Experimentally, we demonstrate the implementation of such a mode and measure the spin density upon propagation. (C) 2016 Optical Society of America
Quantum-polarization state tomography
Oemer Bayraktar,
Marcin Swillo,
Carlota Canalias,
Gunnar Bjork
We propose and demonstrate a method for quantum-state tomography of qudits encoded in the quantum polarization of N-photon states. This is achieved by distributing N photons nondeterministically into three paths and their subsequent projection, which for N = 1 is equivalent to measuring the Stokes (or Pauli) operators. The statistics of the recorded N-fold coincidences determines the unknown N-photon polarization state uniquely. The proposed, fixed setup manifestly rules out any systematic measurement errors due to moving components and allows for simple switching between tomography of different states, which makes it ideal for adaptive tomography schemes.
Polarization Beat Length Estimation Based on the Statistical Properties
of Brillouin Gain in SMF
A simple method is proposed to estimate the average polarization beat length of single mode fiber (SMF) through the analysis of statistical characteristics of stimulated Brillouin amplified signals. Through launching a variety of pump wave polarizations, the standard deviation of the Brillouin gain is found linearly related with the fiber beat length, within the normal range of beat length values for SMFs. Both the numerical simulations and the experimental results are presented to test the validity of the method. The technique reported here offers a fast, convenient, and low-cost solution to estimate fiber average beat length.
Influence of stimulated Brillouin scattering on positioning accuracy of
long-range dual Mach-Zehnder interferometric vibration sensors
Xiangge He,
Shangran Xie,
Shan Cao,
Fei Liu,
Xiaoping Zheng,
Min Zhang,
Han Yan,
Guocai Chen
The possibility of focusing light to an ever tighter spot has important implications for many applications and fields of optics research, such as nano-optics and plasmonics, laser-scanning microscopy, optical data storage, and many more. The size of lateral features of the field at the focus depends on several parameters, including the numerical aperture of the focusing system, but also the wavelength and polarization, phase and intensity distribution of the input beam. Here, we study the smallest achievable focal feature sizes of coherent superpositions of two copropagating beams carrying opposite orbital angular momentum. We investigate the feature sizes for this class of beams not only in the scalar limit, but also use a fully vectorial treatment to discuss the case of tight focusing. Both our numerical simulations and our experimental results confirm that lateral feature sizes considerably smaller than those of a tightly focused Gaussian light beam can be observed. These findings may pave the way for improving the resolution of imaging systems or may find applications in nano-optics experiments.
The squeezing spectrum of a quantum emitter coupled to an optical
nanostructure
We analyze the spectral properties of the reduced quantum fluctuations arising from a single two-level emitter coupled to an optical nanostructure. A closed expression for the squeezing spectrum in this hybrid system is presented that includes the effect of additional phase decoherence. We consider a metallic nanoantenna to illustrate how the hybrid system can increase the bandwidth and overcome the limits to the generation of such spectral squeezing in terms of driving field intensity and the effect of pure dephasing.
Optically assisted trapping with high-permittivity dielectric rings:
Towards optical aerosol filtration
Rasoul Alaee,
Muamer Kadic,
Carsten Rockstuhl,
Ali Passian
Continuously twisted solid-core photonic crystal fiber (PCF) exhibits pure circular birefringence (optical activity), making it ideal for current sensors based on the Faraday effect. By numerical analysis, we identify the PCF geometry for which the circular birefringence (which scales linearly with twist rate) is a maximum. For silica-air PCF, this occurs at a shape parameter (diameter-to-spacing ratio of the hollow channels) of 0.37 and a scale parameter (spacing-to-wavelength) of 1.51. This result is confirmed experimentally by testing a range of different structures. To demonstrate the effectiveness of twisted PCF as a current sensor, a length of fiber is placed on the axis of a 7.6 cm long solenoid, and the Faraday rotation is measured at different values of dc current. The system is then used to chart the wavelength dependence of the Verdet constant. (C) 2016 Optical Society of America
Twist-induced guidance in coreless photonic crystal fiber: A helical
channel for light
Ramin Beravat,
Gordon K. L. Wong,
Michael H. Frosz,
Xiao Ming Xi,
Philip St. J. Russell
We investigate polarization squeezing in squeezed coherent states with varying coherent amplitudes. In contrast to the traditional characterization based on the full Stokes parameters, we experimentally determine the Stokes vector of each excitation subspace separately. Only for states with a fixed photon number do the methods coincide; when the photon number is indefinite, we parse the state in Fock layers, finding that substantially higher squeezing can be observed in some of the single layers. By capitalizing on the properties of the Husimi Q function, we map this notion onto the Poincare space, providing a full account of the measured squeezing.
Implementing a neutral-atom controlled-phase gate with a single Rydberg
pulse
One can implement fast two-qubit entangling gates by exploiting the Rydberg blockade. Although various theoretical schemes have been proposed, experimenters have not yet been able to demonstrate two-atom gates of high fidelity due to experimental constraints. We propose a novel scheme, which only uses a single Rydberg pulse illuminating both atoms, for the construction of neutral-atom controlled-phase gates. In contrast to the existing schemes, our approach is simpler to implement and requires neither individual addressing of atoms nor adiabatic procedures. With parameters estimated based on actual experimental scenarios, a gate fidelity higher than 0.99 is achievable. Copyright (C) EPLA, 2016
Optical resolution from Fisher information
L. Motka,
B. Stoklasa,
M. D'Angelo,
P. Facchi,
A. Garuccio,
Z. Hradil,
S. Pascazio,
F. V. Pepe,
Y. S. Teo, et al.
EUROPEAN PHYSICAL JOURNAL PLUS
131
(5)
130
(2016)
| Journal
Optically Driven Self-Oscillations of a Silica Nanospike at Low Gas
Pressures
Shangran Xie,
Riccardo Pennetta,
Roman E. Noskov,
Philip St. J. Russell
OPTICAL TRAPPING AND OPTICAL MICROMANIPULATION XIII
UNSP 99220A
(2016)
| Journal
Nanoscale Characterization of Carrier Dynamic and Surface Passivation in
InGaN/GaN Multiple Quantum Wells on GaN Nanorods
Weijian Chen,
Xiaoming Wen,
Michael Latzel,
Martin Heilmann,
Jianfeng Yang,
Xi Dai,
Shujuan Huang,
Santosh Shrestha,
Robert Patterson, et al.
Dielectric tuning and coupling of whispering gallery modes using an
anisotropic prism
Matthew R. Foreman,
Florian Sedlmeir,
Harald G. L. Schwefel,
Gerd Leuchs
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
33
(11)
2177-2195
(2016)
| Journal
Two-Color Coherent Control of Femtosecond Above-Threshold Photoemission
from a Tungsten Nanotip
Michael Foerster,
Timo Paschen,
Michael Krueger,
Christoph Lemell,
Georg Wachter,
Florian Libisch,
Thomas Madlener,
Joachim Burgdoerfer,
Peter Hommelhoff
Visualization and ligand-induced modulation of dopamine receptor
dimerization at the single molecule level
Alina Tabor,
Siegfried Weisenburger,
Ashutosh Banerjee,
Nirupam Purkayastha,
Jonas M. Kaindl,
Harald Huebner,
Luxi Wei,
Teja W. Groemer,
Johannes Kornhuber, et al.
G protein–coupled receptors (GPCRs), including dopamine receptors, represent a group of important pharmacological targets. An increased formation of dopamine receptor D2 homodimers has been suggested to be associated with the pathophysiology of schizophrenia. Selective labeling and ligand-induced modulation of dimerization may therefore allow the investigation of the pathophysiological role of these dimers. Using TIRF microscopy at the single molecule level, transient formation of homodimers of dopamine receptors in the membrane of stably transfected CHO cells has been observed. The equilibrium between dimers and monomers was modulated by the binding of ligands; whereas antagonists showed a ratio that was identical to that of unliganded receptors, agonist-bound D2 receptor-ligand complexes resulted in an increase in dimerization. Addition of bivalent D2 receptor ligands also resulted in a large increase in D2 receptor dimers. A physical interaction between the protomers was confirmed using high resolution cryogenic localization microscopy, with ca. 9 nm between the centers of mass.
Polaritonic normal-mode splitting and light localization in a one-dimensional nanoguide
We theoretically investigate the interaction of light and a collection of emitters in a subwavelength one-dimensional medium (nanoguide), where enhanced emitter-photon coupling leads to efficient multiple scattering of photons. We show that the spectrum of the transmitted light undergoes normal-mode splitting even though no external cavity resonance is employed. By considering densities much higher than those encountered in cold atom experiments, we study the influence of the near-field dipole coupling and disorder on the resulting complex super-radiant and subradiant polaritonic states. In particular, we provide evidence for the longitudinal localization of light in a one-dimensional open system and provide a polaritonic phase diagram. Our results motivate a number of experiments, where new coherent superposition states of light and matter can be realized in the solid state.
Efficient Common-Mode Noise Suppression for Fiber-Optic Interferometric
Sensor Using Heterodyne Demodulation
Fei Liu,
Shangran Xie,
Xiaokang Qiu,
Xiaofei Wang,
Shan Cao,
Mengzhe Qin,
Xiangge He,
Bin Xie,
Xiaoping Zheng, et al.
JOURNAL OF LIGHTWAVE TECHNOLOGY
34
(23)
5453-5461
(2016)
| Journal
Self-alignment of glass fiber nanospike by optomechanical back-action in hollow-core photonic crystal fiber
A topic of great current interest is the harnessing and enhancement of optical tweezer forces for trapping small objects of different sizes and shapes at relatively small powers. Here we demonstrate the stable trapping, inside the core of a hollow-core photonic crystal fiber (HC-PCF), of a mechanically compliant fused silica nanospike, formed by tapering a single-mode fiber (SMF). The nanospike is subwavelength in diameter over its similar to W50 mu m insertion length in the HC-PCF. Laser light, launched into the SMF core, adiabatically evolves into a mode that extends strongly into the space surrounding the nanospike. It then senses the presence of the hollow core, and the resulting optomechanical action and back-action results in a strong trapping force at the core center. The system permits lens-less, reflection-free, self-stabilized, and self-aligned coupling from SMF to HC-PCF with a demonstrated efficiency of 87.8%. The unique configuration also provides an elegant means of investigating optomechanical effects in optical tweezers, especially at very low pressures. (C) 2016 Optical Society of America
The response of cells to toxins is commonly investigated by detecting intracellular markers for cell death, such as caspase proteins. This requires the introduction of labels by the permeabilization or complete lysis of cells. Here we introduce a non-invasive tool for monitoring a caspase protein in the extracellular medium. The tool is based on highly sensitive optical micro-devices, referred to as whispering-gallery mode biosensors (WGMBs). WGMBs are functionalized with antibodies for the specific and label-free detection of procaspase-3 released from human embryonic kidney HEK293 and neuroglioma H4 cells after introducing staurosporine and rotenone toxins, respectively. Additional tests show that the extracellular accumulation of procaspase-3 is concomitant with a decrease in cell viability. The hitherto unknown release of procaspase-3 from cells in response to toxins and its accumulation in the medium is further investigated by Western blot, showing that the extracellular detection of procaspase-3 is interrelated with cytotoxicity of alpha-synuclein protein (aSyn) overexpressed in H4 cells. These studies provide evidence for procaspase-3 as a novel extracellular biomarker for cell death, with applications in cytotoxicity tests. Such WGMBs could be applied to further identify as-yet unknown extracellular biomarkers using established antibodies against intracellular antigens.
Broadband robustly single-mode hollow-core PCF by resonant filtering of
higher-order modes
Patrick Uebel,
Mehmet C. Guenendi,
Michael H. Frosz,
Goran Ahmed,
Nitin N. Edavalath,
Jean-Michel Menard,
Philip St. J. Russell
We report a hollow-core photonic crystal fiber that is engineered so as to strongly suppress higher-order modes, i.e., to provide robust LP01 single-mode guidance in all the wavelength ranges where the fiber guides with low loss. Encircling the core is a single ring of nontouching glass elements whose modes are tailored to ensure resonant phase-matched coupling to higher-order core modes. We show that the resulting modal filtering effect depends on only one dimensionless shape parameter, akin to the well-known d/Lambda parameter for endlessly single-mode solid-core PCF. Fabricated fibers show higher-order mode losses some similar to 100 higher than for the LP01 mode, with LP01 losses <0.2 dB/m in the near-infrared and a spectral flatness similar to 1 dB over a >110 THz bandwidth. (C) 2016 Optical Society of America
Heralded source of bright multi-mode mesoscopic sub-Poissonian light
T. Sh. Iskhakov,
V. C. Usenko,
U. L. Andersen,
R. Filip,
M. V. Chekhova,
G. Leuchs
In a direct detection scheme, we observed 7.8 dB of twin-beam squeezing for multi-mode two-color squeezed vacuum generated via parametric downconversion. Applying postselection, we conditionally prepared a sub-Poissonian state of light containing 6.3 . 10(5) photons per pulse on the average with the Fano factor 0.63 +/- 0.01. The scheme can be considered as the heralded preparation of pulses with the mean energy varying between tens and hundreds of fJ and the uncertainty considerably below the shot-noise level. Such pulses can be used in metrology (for instance, for radiometer calibration), as well as for probing multi-mode non-linear optical effects. (C) 2016 Optical Society of America
Polarization-controlled directional scattering for nanoscopic position
sensing
Martin Neugebauer,
Pawel Wozniak,
Ankan Bag,
Gerd Leuchs,
Peter Banzer
Controlling the propagation and coupling of light to sub-wavelength antennas is a crucial prerequisite for many nanoscale optical devices. Recently, the main focus of attention has been directed towards high-refractive-index materials such as silicon as an integral part of the antenna design. This development is motivated by the rich spectral properties of individual high-refractive-index nanoparticles. Here we take advantage of the interference of their magnetic and electric resonances to achieve strong lateral directionality. For controlled excitation of a spherical silicon nanoantenna, we use tightly focused radially polarized light. The resultant directional emission depends on the antenna's position relative to the focus. This approach finds application as a novel position sensing technique, which might be implemented in modern nanometrology and super-resolution microscopy set-ups. We demonstrate in a proof-of-concept experiment that a lateral resolution in the Angstrom regime can be achieved.
Maximizing Photoluminescence Extraction in Silicon Photonic Crystal
Slabs
Ali Mahdavi,
George Sarau,
Jolly Xavier,
Taofiq K. Paraiso,
Silke Christiansen,
Frank Vollmer
Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported.
Design of tunable GHz-frequency optomechanical crystal resonators
Hannes Pfeifer,
Taofiq Paraiso,
Leyun Zang,
Oskar Painter
We present a silicon optomechanical nanobeam design with a dynamically tunable acoustic mode at 10.2 GHz. The resonance frequency can be shifted by 90 kHz/V-2 with an on-chip capacitor that was optimized to exert forces up to 1 mu N at 10 V operation voltage. Optical resonance frequencies around 190 THz with Q-factors up to 2.2 x 10(6) place the structure in the well-resolved sideband regime with vacuum optomechanical coupling rates up to g(0)/2 pi = 353 kHz. Tuning can be used, for instance, to overcome variation in the device-to-device acoustic resonance frequency due to fabrication errors, paving the way for optomechanical circuits consisting of arrays of optomechanical cavities. (C) 2016 Optical Society of America
Frequency tuning of single photons from a whispering-gallery mode
resonator to MHz-wide transitions
G. Schunk,
U. Vogl,
F. Sedlmeir,
D. V. Strekalov,
A. Otterpohl,
V. Averchenko,
H. G. L. Schwefel,
G. Leuchs,
Ch. Marquardt
Exotic looped trajectories of photons in three-slit interference
Omar S. Magana-Loaiza,
Israel De Leon,
Mohammad Mirhosseini,
Robert Fickler,
Akbar Safari,
Uwe Mick,
Brian McIntyre,
Peter Banzer,
Brandon Rodenburg, et al.
JOURNAL OF RUSSIAN LASER RESEARCH
37
(6)
556-561
(2016)
| Journal
Visualization of lipids and proteins at high spatial and temporal
resolution via interferometric scattering (iSCAT) microscopy
Susann Spindler,
Jens Ehrig,
Katharina König,
Tristan Nowak,
Marek Piliarik,
Hannah E. Stein,
Richard W. Taylor,
Elisabeth Garanger,
Sebastien Lecommandoux, et al.
Journal of Physics D - Applied Physics
49
274002
(2016)
| Journal
Microscopy based on the interferometric detection of light scattered from nanoparticles (iSCAT) was introduced in our laboratory more than a decade ago. In this work, we present various capabilities of iSCAT for biological studies by discussing a selection of our recent results. In particular, we show tracking of lipid molecules in supported lipid bilayers (SLBs), tracking of gold nanoparticles with diameters as small as 5 nm and at frame rates close to 1 MHz, 3D tracking of Tat peptide-coated nanoparticles on giant unilamellar vesicles (GUVs), imaging the formation of lipid bilayers, sensing single unlabelled proteins and tracking their motion under electric fields, as well as challenges of studying live cell membranes. These studies set the ground for future quantitative research on dynamic biophysical processes at the nanometer scale.
Visualization of lipids and proteins at high spatial and temporal resolution via interferometric scattering (iSCAT) microscopy
Susann Spindler,
Jens Ehrig,
Katharina Koenig,
Tristan Nowak,
Marek Piliarik,
Hannah E. Stein,
Richard W. Taylor,
Elisabeth Garanger,
Sebastien Lecommandoux, et al.
Microscopy based on the interferometric detection of light scattered from nanoparticles (iSCAT) was introduced in our laboratory more than a decade ago. In this work, we present various capabilities of iSCAT for biological studies by discussing a selection of our recent results. In particular, we show tracking of lipid molecules in supported lipid bilayers (SLBs), tracking of gold nanoparticles with diameters as small as 5 nm and at frame rates close to 1 MHz, 3D tracking of Tat peptide-coated nanoparticles on giant unilamellar vesicles (GUVs), imaging the formation of lipid bilayers, sensing single unlabelled proteins and tracking their motion under electric fields, as well as challenges of studying live cell membranes. These studies set the ground for future quantitative research on dynamic biophysical processes at the nanometer scale.
Partially Hydrated Electrons at the Air/Water Interface Observed by
UV-Excited Time-Resolved Heterodyne-Detected Vibrational Sum Frequency
Generation Spectroscopy
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
138
(24)
7551-7557
(2016)
| Journal
Hydrated electrons are the most fundamental anion species, consisting only of electrons and surrounding water molecules. Although hydrated electrons have been extensively studied in the bulk aqueous solutions, even their existence is still controversial at the water surface. Here, we report the observation and characterization of hydrated electrons at the air/water interface using new time-resolved interface-selective nonlinear vibrational spectroscopy. With the generation of electrons at the air/water interface by ultraviolet photoirradiation, we observed the appearance of a strong transient band in the OH stretch region by heterodyne-detected vibrational sum-frequency generation. Through the comparison with the time-resolved spectra at the air/indole solution interface, the transient band was assigned to the vibration of water molecules that solvate electrons at the interface. The analysis of the frequency and decay of the observed transient band indicated that the electrons are only partially hydrated at the water surface, and that they escape into the bulk within 100 ps.
Pushing the Photon Limit: Nanoantennas Increase Maximal Photon Stream
and Total Photon Number
Emilie Wientjes,
Jan Renger,
Richard Cogdell,
Niek F. van Hulst
Nanoantennas are well-known for their effective role in fluorescence enhancement, both in excitation and emission. Enhancements of 3-4 orders of magnitude have been reported. Yet in practice, the photon emission is limited by saturation due to the time that a molecule spends in singlet and especially triplet excited states. The maximal photon stream restricts the attainable enhancement. Furthermore, the total number of photons emitted is limited by photobleaching. The limited brightness and observation time are a drawback for applications, especially in biology. Here we challenge this photon limit, showing that nanoantennas can actually increase both saturation intensity and photostability. So far, this limit-shifting role of nanoantennas has hardly been explored. Specifically, we demonstrate that single light-harvesting complexes, under saturating excitation conditions, show over a 50-fold antenna-enhanced photon emission stream, with 10-fold more total photons, up to 108 detected photons, before photobleaching. This work shows yet another facet of the great potential of nanoantennas in the world of single-molecule biology.
All-optical bit storage in a fibre laser by optomechanically bound states of solitons
Soliton fibre lasers mode-locked at a high harmonic of their round-trip frequency have many potential applications, from telecommunications to data storage(1). Control of multiple pulses in passively mode-locked fibre lasers has, however, proved very difficult to achieve. This has recently changed with the advent of fibre lasers mode-locked by intense optomechanical interactions in a short length of photonic crystal fibre(2,3). Optomechanical coupling between cavity modes gives rise to highly stable, optomechanically bound, laser soliton states. The repetition rate of these states corresponds to the mechanical resonant frequency in the photonic crystal fibre core(4), which can be a few gigahertz. Here we show that this system can be successfully used for programmable generation and storage of gigahertz-rate soliton sequences over many hours.
Quantum technology: from research to application
Wolfgang P. Schleich,
Kedar S. Ranade,
Christian Anton,
Markus Arndt,
Markus Aspelmeyer,
Manfred Bayer,
Gunnar Berg,
Tommaso Calarco,
Harald Fuchs, et al.
The term quantum physics refers to the phenomena and characteristics of atomic and subatomic systems which cannot be explained by classical physics. Quantum physics has had a long tradition in Germany, going back nearly 100 years. Quantum physics is the foundation of many modern technologies. The first generation of quantum technology provides the basis for key areas such as semiconductor and laser technology. The "new" quantum technology, based on influencing individual quantum systems, has been the subject of research for about the last 20 years. Quantum technology has great economic potential due to its extensive research programs conducted in specialized quantum technology centres throughout the world. To be a viable and active participant in the economic potential of this field, the research infrastructure in Germany should be improved to facilitate more investigations in quantum technology research.
Local Sampling of the Wigner Function at Telecom Wavelength with
Loss-Tolerant Detection of Photon Statistics
G. Harder,
Ch Silberhorn,
J. Rehacek,
Z. Hradil,
L. Motka,
B. Stoklasa,
L. L. Sanchez-Soto
We report the experimental point-by-point sampling of the Wigner function for nonclassical states created in an ultrafast pulsed type-II parametric down-conversion source. We use a loss-tolerant time-multiplexed detector based on a fiber-optical setup and a pair of photon-number-resolving avalanche photodiodes. By capitalizing on an expedient data-pattern tomography, we assess the properties of the light states with outstanding accuracy. The method allows us to reliably infer the squeezing of genuine two-mode states without any phase reference.
Composite Nanostructures of TiO2 and ZnO for Water Splitting
Application: Atomic Layer Deposition Growth and Density Functional
Theory Investigation
Marina Kulmas,
Leanne Paterson,
Katja Hoeflich,
Muhammad Y. Bashouti,
Yanlin Wu,
Manuela Goebelt,
Juergen Ristein,
Julien Bachmann,
Bernd Meyer, et al.
The commercialization of solar fuel devices requires the development of novel engineered photoelectrodes for water splitting applications which are based on redundant, cheap, and environmentally friendly materials. In the current study, a combination of titanium dioxide (TiO2) and zinc oxide (ZnO) onto nanotextured silicon is utilized for a composite electrode with the aim to overcome the individual shortcomings of the respective materials. The properties of conformal coverage of TiO2 and ZnO layers are designed on the atomic scale by the atomic layer deposition technique. The resulting photoanode shows not only promising stability but also nine times higher photocurrents than an equivalent photoanode with a pure TiO2 encapsulation onto the nanostructured silicon. Density functional theory calculations indicate that segregation of TiO2 at the ZnO surfaces is favorable and leads to the stabilization of the ZnO layers in water environments. In conclusion, the novel designed composite material constitutes a promising base for a stable and effective photoanode for the water oxidation reaction.
Low-noise macroscopic twin beams
Timur Sh. Iskhakov,
Vladyslav C. Usenko,
Radim Filip,
Maria V. Chekhova,
Gerd Leuchs
Applying a multiphoton-subtraction technique to the two-color macroscopic squeezed vacuum state of light generated via high-gain parametric down-conversion we conditionally prepare a different state of light: bright multimode low-noise twin beams. A lower noise in the sum of the photon numbers opens a possibility to encode information into this variable while keeping the nonclassical character of the state. The obtained results demonstrate up to eightfold suppression of noise in each beam while preserving and even moderately improving the nonclassical photon-number correlations between the beams. The prepared low-noise macroscopic state, containing up to 2000 photons per mode, is not among the Gaussian states achievable through nonlinear optical processes. Apart from that, we suggest a method for measuring quantum efficiency, which is based on the Fano factor measurement. The proposed technique substantially improves the usefulness of twin beams for quantum communication and metrology.
Expansion of arbitrary electromagnetic fields in terms of vector
spherical wave functions
Wendel Lopes Moreira,
Antonio Alvaro Ranha Neves,
Martin K. Garbos,
Tijmen G. Euser,
Carlos Lenz Cesar
Since 1908, when Mie reported analytical expressions for the fields scattered by a spherical particle upon incidence of plane-waves, generalizing his analysis for the case of an arbitrary incident wave has been an open question because of the cancellation of the prefactor radial spherical Bessel function. This cancellation was obtained before by our own group for a highly focused beam centered in the objective. In this work, however, we show for the first time how these terms can be canceled out for any arbitrary incident field that satisfies Maxwells equations, and obtain analytical expressions for the beam shape coefficients. We show several examples on how to use our method to obtain analytical beam shape coefficients for: Bessel beams, general hollow waveguide modes and specific geometries such as cylindrical and rectangular. Our method uses the vector potential, which shows the interesting characteristic of being gauge invariant. These results are highly relevant for speeding up numerical calculation of light scattering applications such as the radiation forces acting on spherical particles placed in an arbitrary electromagnetic field, as in an optical tweezers system. (C) 2016 Optical Society of America
Generation of a vacuum ultraviolet to visible Raman frequency comb in
H-2-filled kagome photonic crystal fiber
M. K. Mridha,
D. Novoa,
S. T. Bauerschmidt,
A. Abdolvand,
P. St J. Russell
We report on the generation of a purely vibrational Raman comb, extending from the vacuum ultraviolet (184 nm) to the visible (478 nm), in hydrogen-filled kagome-style photonic crystal fiber pumped at 266 nm. Stimulated Raman scattering and molecular modulation processes are enhanced by higher Raman gain in the ultraviolet. Owing to the pressure-tunable normal dispersion landscape of the "fiber + gas" system in the ultraviolet, higher-order anti-Stokes bands are generated preferentially in higher-order fiber modes. The results pave the way toward tunable fiber-based sources of deep and vacuum ultraviolet light for applications in, e.g., spectroscopy and biomedicine. (C) 2016 Optical Society of America
Broadband electric-field-induced LP01 and LP02 second harmonic
generation in Xe-filled hollow-core PCF
Jean-Michel Menard,
Felix Köttig,
Philip St. J. Russell
Second harmonic (SH) generation with 300 fs pump pulses is reported in a xenon-filled hollow-core photonic crystal fiber (PCF) across which an external bias voltage is applied. Phase-matched intermodal conversion from a pump light in the LP01 mode to SH light in the LP02 mode is achieved at a particular gas pressure. Using periodic electrodes, quasi-phase-matched SH generation into the low-loss LP01 mode is achieved at a different pressure. The low linear dispersion of the gas enables phase-matching over a broad spectral window, resulting in a measured bandwidth of similar to 10 nm at high pump energies. A conversion efficiency of similar to 18%/ mJ is obtained. Gas-filled anti-resonant-reflecting hollow-core PCF uniquely offers pressure-tunable phase-matching, ultra-broadband guidance, and a very high optical damage threshold, which hold great promise for efficient three-wave mixing, especially in difficult-to-access regions of the electromagnetic spectrum. (C) 2016 Optical Society of America
Nonlinear interferometer for tailoring the frequency spectrum of bright squeezed vacuum
T. Sh. Iskhakov,
S. Lemieux,
A. Perez,
R. W. Boyd,
G. Leuchs,
M. V. Chekhova
JOURNAL OF MODERN OPTICS
63
(1 SI)
64-70
(2016)
| Journal
We propose a method for tailoring the frequency spectrum of bright squeezed vacuum by generating it in a nonlinear interferometer, consisting of two down-converting nonlinear crystals separated by a dispersive medium. Due to a faster dispersive spreading of higher order Schmidt modes, the spectral width of the radiation at the output is reduced as the length of the dispersive medium is increased. Preliminary results show 30% spectral narrowing.
Understanding Charge Transport in Mixed Networks of Semiconducting
Carbon Nanotubes
Marcel Rother,
Stefan P. Schiessi,
Yuriy Zakharko,
Florentina Gannott,
Jana Zaumseil
The ability to select and enrich semiconducting single-walled carbon nanotubes (SWNT) with high purity has led to a fast rise of solution-processed nanotube network field-effect transistors (FETs) with high carrier mobilities and on/off current ratios. However, it remains an open question whether it is best to use a network of only one nanotube species (monochiral) or whether a mix of purely semiconducting nanotubes but with different bandgaps is sufficient for high performance FETs. For a range of different polymer-sorted semiconducting SWNT networks, we demonstrate that a very small amount of narrow bandgap nanotubes within a dense network of large bandgap nanotubes can dominate the transport and thus severely limit on-currents and effective carrier mobility. Using, gate-voltage dependent electroluminescence, we spatially and spectrally reveal preferential charge transport:that toes not depend on nominal network density but on the energy level distribution within the network and carrier density. On the basis of these results, we outline rational guidelines for the use of mixed SWNT networks to obtain high performance FETs while reducing the cost for purification.
Topological phase transitions and chiral inelastic transport induced by
the squeezing of light
Vittorio Peano,
Martin Houde,
Christian Brendel,
Florian Marquardt,
Aashish A. Clerk
Nature Communications
7
10779
(2016)
| Journal
| PDF
There is enormous interest in engineering topological photonic systems. Despite intense activity, most works on topological photonic states (and more generally bosonic states) amount in the end to replicating a well-known fermionic single-particle Hamiltonian. Here we show how the squeezing of light can lead to the formation of qualitatively new kinds of topological states. Such states are characterized by non-trivial Chern numbers, and exhibit protected edge modes, which give rise to chiral elastic and inelastic photon transport. These topological bosonic states are not equivalent to their fermionic (topological superconductor) counterparts and, in addition, cannot be mapped by a local transformation onto topological states found in particle-conserving models. They thus represent a new type of topological system. We study this physics in detail in the case of a kagome lattice model, and discuss possible realizations using nonlinear photonic crystals or superconducting circuits.
Noise-induced transitions in optomechanical synchronization
Talitha Weiss,
Andreas Kronwald,
Florian Marquardt
New Journal of Physics
18
013043
(2016)
| Journal
| PDF
We study how quantum and thermal noise affects synchronization of two optomechanical limit-cycle oscillators. Classically, in the absence of noise, optomechanical systems tend to synchronize either in-phase or anti-phase. Taking into account the fundamental quantum noise, we find a regime where fluctuations drive transitions between these classical synchronization states. We investigate how this 'mixed' synchronization regime emerges from the noiseless system by studying the classical-to-quantum crossover and we show how the time scales of the transitions vary with the effective noise strength. In addition, we compare the effects of thermal noise to the effects of quantum noise.
Few-photon coherent nonlinear optics with a single molecule
Andreas Maser,
Benjamin Gmeiner,
Tobias Utikal,
Stephan Goetzinger,
Vahid Sandoghdar
The pioneering experiments in linear spectroscopy were performed using flames in the 1800s, but nonlinear optical measurements had to wait until lasers became available in the twentieth century. Because the nonlinear cross-section of materials is very small(1,2), macroscopic bulk samples and pulsed lasers are usually used. Numerous efforts have explored coherent nonlinear signal generation from individual nanoparticles(3-5) or small atomic ensembles(6-8) with millions of atoms. Experiments on a single semiconductor quantum dot have also been reported, albeit with a very small yield(9). Here, we report the coherent nonlinear spectroscopy of a single molecule under continuous-wave single-pass illumination and the switching of a laser beam by on the order of ten pump photons. The sharp molecular transitions and efficient photon-molecule coupling at a tight focus(10) allow for optical switching with less than a handful of pump photons and are thus promising for applications in quantum engineering(11).
Spectroscopy and microscopy of single molecules in nanoscopic channels:
spectral behavior vs. confinement depth
Benjamin Gmeiner,
Andreas Maser,
Tobias Utikal,
Stephan Goetzinger,
Vahid Sandoghdar
Physical Chemistry Chemical Physics
18
19588-19594
(2016)
| Journal
We perform high-resolution spectroscopy and localization microscopy to study single dye molecules confined to nanoscopic dimensions in one direction. We provide the fabrication details of our nanoscopic glass channels and the procedure for filling them with organic matrices. Optical data on hundreds of molecules in different channel depths show a clear trend from narrow stable lines in deep channels to broader linewidths in ultrathin matrices. In addition, we observe a steady blue shift of the center of the inhomogeneous band as the channels become thinner. Furthermore, we use super-resolution localization microscopy to correlate the positions and orientations of the individual dye molecules with the lateral landscape of the organic matrix, including cracks and strain-induced dislocations. Our results and methodology are useful for a number of studies in various fields such as physical chemistry, solid-state spectroscopy, and quantum nano-optics.
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