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Coherent Beam Combing of Lasers Generated by Optical Parametric Oscillators

Feng Liwen, Xiao-Jun Wang, and Weiwei Ke

Doc ID: 285085 Received 19 Jan 2017; Accepted 25 Mar 2017; Posted 27 Mar 2017  View: PDF

Abstract: We propose a possible way to achieve the coherent beam combination (CBC) for lasers generated by optical parametric process. We point out that the essential difficulty is to lock the phase of an individual wave in the three-wave mixing process. The phase evolution law in optical parametric amplifier (OPA) for both cases of phase matching and quasi-phase matching is studied theoretically. The results indicate that, under the condition of strong pumping, higher intensity injection signal can lock its phase to be its initial value, while for weaker injection signal the phases of the signal and idler waves exhibit chaos-like evolution. Based on this understanding, we propose a ring configuration for optical parametric oscillator (OPO) with the appropriate intensity seed injection. The numerical studies indicate this OPO configuration can achieve the phase-locking and wavelength-locking simultaneously. This inspires a possible design to achieve CBC of OPO lasers.

Generation of high Energy Femtosecond Pulses by use of spectral Broadening Effects in Yb:YAG Thin Disk Regenerative Amplifiers

Joerg Neuhaus, Florian Fink, and Mikhail Larionov

Doc ID: 283513 Received 22 Dec 2016; Accepted 23 Mar 2017; Posted 24 Mar 2017  View: PDF

Abstract: As a result of experimentally verified simulations of Yb:YAG regenerative amplifiers utilizing spectral broadening effects due to self-phase modulation (SPM), we provide a map for the optimized choice of initial chirp and internal group-delay dispersion (GDD) within the amplifier. We show that the shortest pulse durations can be obtained with negative internal GDD within the regenerative amplifier, however being limited by the damage threshold of the optical components due to increased peak powers within the amplifier and by a break-up of pulses comparable to the propagation of higher order solitons.We propose that by usage of increasing amounts of positive internal GDD along with a corresponding amount of negative initial GDD, the obtainable peak powers after compression can be scaled far beyond the usual gain bandwidth limitation.

Differential Global Surface Impedance (DGSI), A Novel Rigorous Model for Analyzing Dielectric Periodic Structures

Hoda Ameri and Reza Faraji-Dana

Doc ID: 282446 Received 08 Dec 2016; Accepted 22 Mar 2017; Posted 23 Mar 2017  View: PDF

Abstract: A new and efficient Differential Global Surface Impedance (DGSI) model has been developed for the analysis of dielectric periodic structures. The proposed rigorous model makes use of equivalence principle to relate the surface electric current and the tangential electric field on the boundary of the object made of a general medium. This approach not only enables one to limit the discretization to the surface of the object located in one unit cell of the structure, but also eliminates the need for equivalent surface magnetic current in applying the equivalence principle. These advantages result in a great reduction in the need for computational resources and time. The use of an efficient periodic Green’s function by employing the Complex Images (CI) technique, combined with the proposed DGSI model, has increased the numerical efficiency of the proposed method. A number of dielectric periodic structures made of array of cylinders with circular or square cross sections have been analyzed by this method. Accuracy of the proposed method, as well as its numerical efficiency have been demonstrated by comparing its results with other methods in the literature employing surface and volume integral equations.

Optical Bessel tractor beam on active dielectric Rayleigh prolate and oblate spheroids

Farid Mitri

Doc ID: 286299 Received 07 Feb 2017; Accepted 21 Mar 2017; Posted 21 Mar 2017  View: PDF

Abstract: Optical Bessel tractor beams designed to produce a negative pulling force on a particle, are gaining increased attention for applications in noncontact remote sampling, particle manipulation and handling to name some examples. In the long-wavelength (Rayleigh) limit, known also as the electric dipole approximation, earlier investigations have demonstrated that a zeroth-order Bessel beam incident upon a passive dielectric sphere (i.e. no radiating sources in its core) always acts as a repulsor beam, which causes the particle to be pushed away from the source in the forward direction of the linear momentum. In contrast to what has already been established, this work shows that the incident wave-field can act as a tractor beam (where the small spheroid is pulled backwards towards the source due to a negative attractive force) in the dipole approximation (Rayleigh) limit, provided that the particle is made of an active material, i.e. a dielectric spheroid acting as an oscillating source for which the extinction energy efficiency is negative. Numerical computations for the Cartesian components of the optical radiation force on active prolate and oblate spheroids with arbitrary orientation are performed. Emphasis is given on the emergence of the tractor beam behavior and its dependence upon the half-cone angle, the polarization type of the incident beam, the spheroid aspect ratio as well as its orientation in space. The analysis is extended to calculate the Cartesian components of the spin radiation torque, which causes a rotation of the spheroid around its center of mass in either the anti-clockwise or the clockwise (negative) direction of spinning. Unlike the case of a sphere, the optical spin torque arises for a non-absorptive oblate or prolate spheroid with arbitrary orientation in the field of a zeroth-order Bessel beam. Potential applications in optically-engineered metamaterials, optical tractor beams, tweezers, particle manipulation, rotation and handling would benefit from the results of this study.

Collapse-induced Orientational Localization of Rigid Rotors

Björn Schrinski, Benjamin Stickler, and Klaus Hornberger

Doc ID: 285850 Received 31 Jan 2017; Accepted 21 Mar 2017; Posted 22 Mar 2017  View: PDF

Abstract: We show how the ro-translational motion of anisotropic particles is affected by the model of Continuous Spontaneous Localization (CSL), the most prominent hypothetical modification of the Schrödinger equation restoring realism on the macroscale. We derive the master equation describing collapse-induced spatio-orientational decoherence, and demonstrate how it leads to linear- and angular-momentum diffusion. Since the associated heating rates scale differently with the CSL parameters, the latter can be determined individually by measuring the random motion of a single levitated nanorotor.

Ultra-High-Finesse NICE-OHMS Spectroscopy at 1532 nm for Calibrated Online Ammonia Detection

E. Anne Curtis, Geoffrey Barwood, Guilong Huang, Christopher Edwards, Bjoern Gieseking, and Paul Brewer

Doc ID: 282451 Received 20 Dec 2016; Accepted 17 Mar 2017; Posted 20 Mar 2017  View: PDF

Abstract: There is increasing industrial demand, particularly within the clean room community, for rapid online measurement of a number of airborne molecular contaminants (AMCs). These measurements are usually made with commercially available cavity ring-down spectrometers, but more recently developed techniques offer potentially better sensitivity and more rapid sampling. In this paper we present ammonia spectroscopy data from a newly-developed NICE-OHMS system at 1532 nm, which is designed to be transportable and operate in an industrial environment. We demonstrate this using an optical cavity of 9 kHz fringe width (~ 1.5 GHz free spectral range and finesse 169,000) and a distributed feedback diode laser with a relatively broad ~ 1 MHz free running linewidth. To our knowledge, this is the highest cavity finesse for which NICE-OHMS has been demonstrated. The variation in NICE-OHMS ammonia signal amplitude is presented at different concentrations in one atmosphere of nitrogen, generated from traceable reference standards, with a flow rate of 1-2 l/min. We derive a calibration curve for our device for concentrations in the range from 100 nmol/mol to 10 µmol/mol.

Simple fringe illumination technique for optical super resolution

Anwar Hussain, Tariq Amin, Cuifang Kuang, Liangcai Cao, and Xu Liu

Doc ID: 282099 Received 02 Dec 2016; Accepted 17 Mar 2017; Posted 21 Mar 2017  View: PDF

Abstract: The simple and precise fringe illumination technique is implemented to retrieve the missing information of two-dimensional object. The object placed in a 4f optical system illuminated with fringes, generated by a reflective-mode Spatial Light Modulator (SLM). A set of three fringes, shifted in phase, sequentially illuminate the object and correspondingly three images are captured through CCD. The fringes illuminate the object and higher spatial frequencies, primarily lies outside the aperture along horizontal direction heterodyne into the pass band. To heterodyne higher spatial frequencies lies in vertical direction, the fringes are swapped by 90 degree and three images captured through CCD. These recorded images processed to retrieve the object information using explicit algorithm. The final image is higher in resolution compared to the band-limited image. For validity of the technique, the theoretical concept simulated and supported with experimental results.

Reflection compensation mediated by electric and magnetic resonances of all-dielectric metasurfaces

Viktoriia Babicheva, Mihail Petrov, Kseniia Baryshnikova, and Pavel Belov

Doc ID: 285987 Received 01 Feb 2017; Accepted 16 Mar 2017; Posted 22 Mar 2017  View: PDF

Abstract: All-dielectric nanostructures have recently emerged as a promising alternative to plasmonic devices, as they also possess pronounced electric and magnetic resonances and allow effective light manipulation. In this work, we study optical properties of a composite structure that consists of a silicon nanoparticle array (metasurface) and high-index substrate aiming at clarifying the role of substrate on reflective properties of the nanoparticles. We develop a simple semi-analytical model that describes interference of separate contributions from nanoparticle array and bare substrate to the total reflection. Applying this model, we show that matching the magnitudes and setting the π-phase difference of the electric and magnetic dipole moments induced in nanoparticles, one can obtain a suppression of reflection from the substrate coated with metasurface. We perform numerical simulations of sphere and disk nanoparticle arrays for different permittivities of the substrate. We find full agreement with the semi-analytical results, which means that the uncoupled-element model adequately describes nanostructure reflective properties, despite the effects of induced bi-anisotropy. The model explains the features of the reflectance spectrum, such as number of dips and their spectral positions, and show why it may not coincide with the spectral positions of Mie resonances of the single nanoparticles forming the system. We also address practical aspects of the antireflective device engineering: we show that the uncoupled-element model is applicable to the structures on top of silicon substrates, including lithographically defined nanopillars. The reflectance suppression from nanoparticle array on top of silicon substrate can be achieved in a broad spectral range with disordered nanoparticle array and for a wide range of incidence angles.

Hybrid plasmon-phonon polariton bands in graphene-hBN metamaterials

Hodjat Hajian, Amir Ghobadi, Sina Abedini Dereshgi, Bayram Butun, and Ekmel Ozbay

Doc ID: 287650 Received 27 Feb 2017; Accepted 16 Mar 2017; Posted 22 Mar 2017  View: PDF

Abstract: We theoretically investigate the mid-infrared electromagnetic wavepropagation in multilayered graphene-hexagonal boron nitride (hBN)metamaterials. Hexagonal boron nitride (hBN) is a natural hyperbolicmaterial that supports highly dispersive phonon-polariton modes intwo Reststrahlen bands with a different type of hyperbolicity. Dueto the hybridization of surface plasmon polaritons of graphene andhyperbolic phonon polaritons of hBN, each isolated unit cell of thegraphene-hBN metamaterial supports hybrid plasmon-phonon polaritons(HPPs). Through the investigation of the band structure of themetamaterial, we find that, due to the coupling between the HPPssupported by each unit, the graphene-hBN metamaterial can supportHPP bands. The dispersion of these bands can be noticeably modifiedfor the different thicknesses of hBN layers leading to theappearance of bands with considerably flat dispersions. Moreover,analysis of light transmission passing through the metamaterialreveals that this system is capable of supporting high-k propagatingHPPs. This characteristic makes the graphene-hBN metamaterials verypromising candidate for the modification of the spontaneous emissionof a quantum emitter, hyperlensing, negative refraction andwaveguiding.

Probing single-photon state tomography using phase-randomized coherent states

Paulo Valente and Arturo Lezama

Doc ID: 282546 Received 09 Dec 2016; Accepted 15 Mar 2017; Posted 21 Mar 2017  View: PDF

Abstract: Quantum processes involving single-photon states are of broad interest in particular for quantum communication. Extending to continuous values a recent proposal by Yuan et al \cite{YUAN16}, we show that single-photon quantum processes can be characterized using phase randomized coherent states (PRCS) as inputs. As a proof of principle, we present the experimental investigation of single-photon tomography using PRCS. The probability distribution of field quadratures measurements for single-photon states can be accurately derived from the PRCS data. As a consequence, the Wigner function and the density matrix of single-photon states are reconstructed with good precision. The sensitivity of the reconstruction to experimental errors and the number of PRCS used is addressed.

Optical vortex with a small core and Gaussian intensity envelope for light-matter interaction

Yisa Rumala and Aaron Leanhardt

Doc ID: 283840 Received 03 Jan 2017; Accepted 15 Mar 2017; Posted 20 Mar 2017  View: PDF

Abstract: Optical vortices with a vortex core size that is at least two orders of magnitude smaller than the laser beam waist is presented. The optical vortex is generated by a spiral phase plate (SPP) and counter-rotating optical vortex pairs are created in a modified Mach-Zehnder interferometer surrounded by a 4$f$ lens arrangement. The azimuthal variation of the counter-rotating optical vortex forms a sinusoidal intensity modulation for which the winding number of the optical vortex is deduced accurately and precisely by fitting it to a sinusoidal function. These results are of interest in designing novel optical vortex gratings for manipulating matter waves (e.g. in Kapitza-Dirac scattering). A theory of atomic angular Kapitza-Dirac scattering with optical vortices is presented. The large beam waist combined with a small optical vortex core size would also be of interest when using an optical vortex to perform spectroscopy in a wide range of matter systems including solid, liquid, atomic, and molecular systems, as well as in short range optical communication.

Azimuthal phase-shifted zone plates to produce petal-like beams and ring-lattice structures

Arash Sabatyan and Jila Rafighdoost

Doc ID: 284824 Received 17 Jan 2017; Accepted 15 Mar 2017; Posted 20 Mar 2017  View: PDF

Abstract: We aim here to present two models zone plates rely on well-known spiral zone plate (SZP). We demonstrate that by given combination of two SZPs with opposite-signed charge strengths novel elements are born whose phase structures are azimuthally shifted and named azimuthal phase shifted zone plates (APZP). Generally speaking, it is illustrated that both of the models have the same diffractive functions. Regarding the topological charge of the superimposed SZPs denoted by $P_1$ and $P_2$, it is demonstrated that petal-like beam and optical ring lattice are created such that if the modulus of $|P_1|-|P_2|$ is being unity the former is generated whilst it is greater than unity the latter is formed. Additionally, the number of petals or lattices is simply manageable and given by $|P_1|+|P_2|$. Defocusing surveys manifest preserving the shape of the beams in a rather long focal depth and also partly rotation of them is also evident. Numerical results are verified by experiments.

Nonparaxial evolution of the Airy-Gaussian vortex beam in uniaxial crystal

Dongdong Li, Xi Peng, Yulian Peng, Liping Zhang, and Dongmei Deng

Doc ID: 280038 Received 10 Jan 2017; Accepted 10 Mar 2017; Posted 13 Mar 2017  View: PDF

Abstract: By generalizing the analytic solutions from the theory of the nonparaxial evolution in uniaxial crystal orthogonal to the optical axis, we investigate analytically and numerically the properties of the nonparaxial evolution of the Airy-Gaussian vortex (AiGV) beam in uniaxial crystal. We study thenonparaxial evolution characteristics of each component, and analyze the effect of the anisotropy of uniaxial crystal and the optical vortex on the AiGV beam evolution. In addition, we also study the influence of the different distribution factor χ0 for the evolution characteristics. We physically attribute these features to the combined contribution of the orbital current and the spin current. Finally, we also analyze the physical mechanism underlying the nonparaxial evolution of the AiGV beam.

Straightforward retrieval of dispersion in dense atomic vapor helped by a buffer gas–assisted radiation channeling

Aram Papoyan, Svetlana Shmavonyan, Davit Khachatryan, and Gayane Grigoryan

Doc ID: 286283 Received 06 Feb 2017; Accepted 09 Mar 2017; Posted 10 Mar 2017  View: PDF

Abstract: Strong enhancement of group refractive index in a dense buffered atomic vapor is recorded using a technique of reflection from a low-finesse Fabry-Pérot cavity filled with dense atomic vapor allowing to retrieve a dispersion curve for the hyperfine structure of Rb D2 line buffered by a high density Cs vapor. Oscillations of the recorded signal resulting from interference of beams reflected from the front and rear windows of the cell appearing with the laser frequency scanning across the resonance allow to easily reconstructing the dispersion curve. Contribution from concomitant interconnected processes, in particular, the determinative role of radiation channeling in enhancement of the resonator Q-factor, is analyzed.

Stimulated Brillouin Scattering in integrated ringresonators

sayyed Reza Mirnaziry, Christian Wolff, Michael Steel, Benjamin Eggleton, and Chris Poulton

Doc ID: 285828 Received 31 Jan 2017; Accepted 06 Mar 2017; Posted 10 Mar 2017  View: PDF

Abstract: We investigate Stimulated Brillouin Scattering (SBS) in ring resonators that exhibit linear and nonlinear losses. We present both analytic and numerical tools that can be used to compute the amplification and lasing threshold for the SBS-induced Stokes line. We show that, for both linear and nonlinear losses, there is a maximum achievable SBS amplification, and we show how this depends on the parameters of the ring and on the material parameters. We also study the relation between the critical coupling and input pump power to achieve amplification in various situations. We present simplified models that can be used to accurately predict the nonlinear behavior of the ring and consequently estimate the pump power required to achieve the optimum gain in a range of technologically important situations.

Strong coupling between a plasmonic waveguide and graphene surface plasmons

Maha Ben Rhouma, Meherzi Oueslati, and Brahim Guizal

Doc ID: 283814 Received 29 Dec 2016; Accepted 05 Mar 2017; Posted 09 Mar 2017  View: PDF

Abstract: We study the coupling between surface plasmons of a doped graphene sheet and those of a Metal- like/Dielectric/Metal-like plasmonic waveguide. In order to allow such a coupling, the metal-like me- dia are chosen to be doped semiconductors with plasma energies close to the Fermi level of the doped graphene. We derive and compute numerically the full dispersion relation and study in details the char- acteristics of the hybrid modes emerging from strong coupling.

Tomographic Phase Microscopy: Principles and Applications in Bioimaging

Di Jin, Renjie Zhou, Zahid Yaqoob, and Peter So

Doc ID: 284340 Received 09 Jan 2017; Accepted 03 Mar 2017; Posted 06 Mar 2017  View: PDF

Abstract: Tomographic phase microscopy (TPM) is an emerging optical microscopic technique for bioimaging. TPM uses digital holographic measurements of complex scattered fields to reconstruct the three-dimensional (3D) refractive index (RI) maps of cells with diffraction-limited resolution by solving the inverse scattering problems. In this paper, we review the developments of TPM from the fundamental physics to its applications in bioimaging. We first give a comprehensive description of the tomographic reconstruction physical models used in TPM. The RI map reconstruction algorithms and various regularization methods are discussed. Selected TPM applications for cellular imaging are reviewed, particularly in hematology. Finally, we examine the limitations in current TPM systems, propose future solutions, and envision promising directions in biomedical research.

Green formulation for studying electromagnetic scattering from graphene--coated wires of arbitrary section

Claudio Valencia, Mauro Cuevas, Eduardo Riso, and Ricardo Depine

Doc ID: 282163 Received 05 Dec 2016; Accepted 20 Feb 2017; Posted 28 Mar 2017  View: PDF

Abstract: We present a rigorous electromagnetic method based on Green’s second identity for studying the plasmonic response of graphene–coated wires of arbitrary shape. The wire is illuminated perpendicular to its axis by a monochromatic electromagnetic wave and the wire substrate is homogeneous and isotropic. The field is expressed everywhere in terms of two unknown source functions evaluated on the graphene coating which can be obtained from the numerical solution of a coupled pair of inhomogeneous integral equations. To assess the validity of the Green formulation, the scattering and absorption efficiencies obtained numerically in the particular case of circular wires are compared with those obtained from the multipolar Mie theory. An excellent agreement is observed in this particular case, both for metallic and dielectric substrates. To explore the effects that the break of the rotational symmetry of the wire section introduces in the plasmonic features of the scattering and absorption response, the Green formulation isapplied to the case of graphene-coated wires of elliptical section. As might be expected from symmetry arguments, we find a two-dimensional anisotropy in the angular optical response of the wire, particularly evident in the frequency splitting of multipolar plasmonic resonances. The comparison between the spectral position of the enhancements in the scattering and absorption efficiency spectra for low–eccentricity elliptical and circular wires allows us to guess the multipolar order of each plasmonic resonance. We present calculations of the near field distribution for different frequencies which explicitly reveal the multipolar order of the plasmonic resonances. They also confirm the previous guess and serve as a further test on the validity of the Green formulation.

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