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Simulations for Transversely diode-pumped metastable rare gas lasers

Jun Gao, yongle he, Pengfei Sun, fan Zhang, Xinbing Wang, and Duluo Zuo

Doc ID: 283391 Received 04 Jan 2017; Accepted 16 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: The transverse pumping geometry simplifies the laser system design by separating pump and laser beams and providing space for multiple diode laser pump sources with poor quality. A transverse pumping double-pass model for metastable rare gas lasers is presented in this paper, in which some intra-cavity information can be obtained. The comparison with Yang’s longitudinally pumped calculation results demonstrated the validity of our model. Several important factors having influence on optical conversion efficiency are simulated and discussed. Simulation of the effects of the required plasma size in transverse pumping model shows that a small size of 0.3×10×10 cm3 is capable of emitting 9 kW with an optical conversion efficiency over 55% and a megawatt-class output would only need an active medium of several litres if the metastable atoms concentration reaches 3×1013cm-3.

A 3-D Modified Gerchberg–Saxton Algorithm Developed for Panoramic Computer Generated Phase-Only Holographic Display

Hsuan-Ting Chang, Chien-Yue Chen, Wu-Chun Li, Chih-Hao Chuang, and Tsung-Jan Chang

Doc ID: 279341 Received 25 Oct 2016; Accepted 14 Feb 2017; Posted 14 Feb 2017  View: PDF

Abstract: In this study, a computer-generated holography based on the three-dimensional (3-D) modified Gerchberg-Saxton algorithm (MGSA) for phase retrieval is proposed and demonstrated in a panoramic projection system. The point-based Fresnel transform is utilized in the MGSA in order to retrieve the panoramic computer-generated phase-only hologram (CGPOH) of a 3-D object. Consider the different viewing angles of the object. The panoramic CGPOH capable of panoramic 3-D projections can be determined by using the rotation matrices and illuminating the light sources at the corresponding viewing angles. The computer simulation and optical experiments are conducted to verify that the determined panoramic CGPOH can successfully generate the panoramic projection images with various depths and under the different viewing angles.

Parabolic trajectory of femtosecond laser filaments generated by accelerating parabolic beams in air

Yuze Hu and Nie Jinsong

Doc ID: 278610 Received 13 Oct 2016; Accepted 14 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Nonlinear dynamics of femtosecond filamentation with accelerating parabolic beams are numerically investigated for the first time. The parabolic trajectory of filaments can be formed in main lobes. For zero order accelerating parabolic beam which contains one wing, the accelerating characteristics of filaments are similar to that of the Airy beam. When it comes to the first order accelerating parabolic beam which consists of two wings with a certain angle between each other, the accelerating action takes place after two main lobes blend together and it can be more obvious with the increase of initial peak intensity. Multiple filaments (MFs) which are formed in the first order accelerating parabolic beam can benefit the accelerating action of filaments and enhance the length of parabolic trajectory. Besides, MFs also raise the possibility for pulse splitting of the main lobe in the temporal domain.

Hyperspectral Holography - novel application of the FT-spectrometer

Sergey Kalenkov, Georgy Kalenkov, and Alexander Shtanko

Doc ID: 282052 Received 02 Dec 2016; Accepted 14 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Novel application of the FT-spectroscopy principles and techniques is suggested - namely, registration of hyperspectral holograms in incoherent light by using FT-spectrometer. This work generalizes and develops our previous results on registration of hyperspectral Fresnel's and image plane holograms. Theoretical and experimental results are provided and discussed. The proposed method is applied to the problems of digital holographic microscopy: speckle noise reduction, hyperspectral imaging and coloring, optical profiling.

Wideband zero-index metacrystal with high transmission at visible frequencies

Jason Li, Zizhuo Liu, and Koray Aydin

Doc ID: 285306 Received 23 Jan 2017; Accepted 13 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Materials with zero-refractive-index exhibit unprecedented optical properties including no spatial phase change and infinitely large phase velocity. Several zero-index material designs including artificial layered metallic/dielectric medium were proposed and demonstrated at microwave, terahertz and IR wavelengths. However, realizing a zero-index material with low-losses, none-dispersion and relatively wide band-width operation at visible frequencies is quite challenging due to optical losses in metals. Here, we propose and numerically demonstrate a three-dimensional zero-index metacrystal (ZIM) with low-loss, low-dispersion and wide-bandwidth at visible frequencies. The ZIM simply consists of periodic Ag nanocube arrays embedded inside a dielectric medium with same lattice constant in all directions. Calculated effective refractive index using parameter retrieval method reveals a relatively wideband (~ 40 nm) of near-zero index (< 0.02) and achromatic behavior for designed metacrystal in the visible frequency. Using full-field electromagnetic simulations, we have theoretically demonstrate that the EM wave always propagates normal to the ZIM-air interface in spite of oblique incidence cases or any arbitrary wavefront of illumination. Our proposed zero-index metacrystal for visible frequencies could find use in many practical applications of wide-bandwidth and low-loss achromatic photonic devices for steering light propagation, arbitrary wavefront conversion, directional emission, and obstacle-free light guiding.

Anomalous reflection of visible light by all-dielectric gradient metasurfaces

Nikolaos Tsitsas and Constantinos Valagiannopoulos

Doc ID: 285933 Received 31 Jan 2017; Accepted 12 Feb 2017; Posted 16 Feb 2017  View: PDF

Abstract: Plane wave scattering by a planar metasurface composed of two periodically alternating rectangular dielectric rods is considered. A rigorous integral equation methodology is employed for the analysis and the accurate determination of the reflected and transmitted fields. Systematic optimizations with respect to the configuration's parameters are performed which reveal that it is possible to obtain significantly enhanced anomalous reflection (with simultaneously suppressed ordinary reflection predicted by Snell's law) with power varying from 92% to almost 100% of the input one, depending on the color of the incident light. It is shown that these reflection properties are supported by metasurfaces easily realizable with specific low-loss dielectric materials. In this way, several all-dielectric optimal designs are reported which can be used in numerous applications demanding anomalous reflection in the visible range.

Microstructural surface characterization of stainless and plain carbon steel using digital holographic microscopy

Ali-Reza Moradi, Yousef Pourvais, Pegah Asgari, Pedram Abdollahi, and Ramin Khamedi

Doc ID: 281972 Received 01 Dec 2016; Accepted 10 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: Scanning probe microscopy techniques are widely applied as three-dimensional (3D) metallography methods in studying metallic microstructures. While providing high lateral and vertical resolutions, these techniques suffer from a limited field-of-view, which is a crucial requirement in many metallurgy studies. Moreover, they are complex and expensive, and need a complicated specimen preparation procedure. In this paper, we introduce reflective digital holographic microscopy for 3D microstructural characterization of metallic surfaces within an adjustable field-of-view and diffraction-limited resolution. Polished and etched CK45 plain carbon steel and AISI 304 stainless steel samples have been studied with the presented method. The experimental results show the capability of the method for metallurgic granular and intergranular studies. The method has the potential to be used in a variety of metallurgic phenomena such as crystal plasticity, microstructural oxidation, and intergranular corrosion.

Decoupling of hyperfine structure of Cs D1 line in strong magnetic field studied by selective reflection from a nanocell

Claude LEROY, Emmanuel Klinger, Ara Tonoyan, David Sarkisyan, Aram Papoyan, Armen Sargsyan, and Grant Hakhumyan

Doc ID: 279857 Received 31 Oct 2016; Accepted 09 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: Decoupling of total electronic and nuclear spin moments of Cs atoms in external magnetic field for the case of atomic D1 line, leading to onset of the hyperfine Paschen-Back regime has been studied theoretically and experimentally. Selective reflection of laser radiation from an interface of dielectric window and atomic vapor confined in a nanocell with 300 nm gap thickness was implemented for the experimental studies. The real time derivative of selective reflection signal with a frequency position coinciding with atomic transitions was used in measurements, providing ~ 40 MHz spectral resolution and linearity of signal response in respect to transition probability. Behavior of 28 individual Zeeman transitions in a wide range of longitudinal magnetic field (0 -- 6 kG) has been tracked under excitation of Cs vapor by a low-intensity σ+ polarized cw laser radiation. For B ≥ 6 kG, only 8 transitions with nearly equal probabilities and the same frequency slope remained in the spectrum, which is a manifestation of the hyperfine Paschen-Back regime. The obtained experimental results are in a very good agreement with numerical modeling. Due to small divergence of selective reflection signal, as well as sub-wavelength thickness and sub-Doppler spectral linewidth inherent to nanocell, the employed technique can be used for distant remote sensing of magnetic field with high spatial and resolution.

Discrete dark solitons in parity-time-symmetric waveguide arrays with gain and loss

Xing Zhu, Huagang Li, Zhiwei Shi, and Tianshu Lai

Doc ID: 278409 Received 10 Oct 2016; Accepted 09 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: We demonstrate that discrete dark solitons can be self-trapped in binary self-defocusingparity-time-symmetric waveguide arrays with gain and loss.The discrete dark solitons appear in the form of a localized dip on the Bloch-wave background.When appropriate boundary condition is satisfied in such finite arrays,the analytical and numerical solutions of discrete dark solitons exist and can both be stable in the one-dimensional case;the stable fundamental discrete vortex solitons can be numerically gained in the two-dimensional case.Interestingly, such one-dimensional discrete dark solitons do not exhibit the displacement properties.

High-order dispersion in Kerr comb oscillators

Changjing Bao, Hossein Taheri, Lin Zhang, Andrey Matsko, Yan Yan, Peicheng Liao, Lute Maleki, and Alan Willner

Doc ID: 280391 Received 08 Nov 2016; Accepted 08 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: We numerically investigate the effect of high-order dispersion on Kerr frequency comb generation in optical microresonators characterized with anomalous group velocity dispersion (GVD) in realistic slot waveguide-based silicon nitride microring and spheroidal crystalline magnesium fluoride resonators. Our numerical simulations indicate that all orders of GVD should be taken into account to obtain the correct envelope shape of the generated Kerr frequency comb. High-order GVD affects the 3-dB comb bandwidth, nonlinear conversion efficiency, and frequency recoil of the comb spectrum (i.e., spectral shift effect), as well as pulse peak power and the power dependence of the pulse timing. Additionally, high-order dispersion terms affect the spectral position of a dispersive wave generated in a microresonator. Our results emphasize the influence of the pump power on the dispersive wave radiation frequency as well as the repetition rate of the generated frequency comb. The latter has significant practical ramifications, for instance for the use of resonator-based frequency combs in optical clocks. We also observe competition in the generation of two different pulses corresponding to nearly the same spectral envelope. These mode-locked combs appear in the presence of a strong anomalous quartic GVD; one of them takes a hyperbolic-secant soliton shape, while the other resembles a Gaussian pulse superimposed on a modulated pedestal. The appearance and stability of the latter pulse depend on the numerical integration technique utilized.

Mid-infrared (4.7 µm) emission from Tb3+ doped selenide-chalcogenide glass and fiber

Lukasz Sojka, ZHUOQI TANG, David Furniss, Hesham Sakr, Elzbieta Beres-Pawlik, Trevor Benson, Angela Seddon, Slawomir Sujecki, and Yuanrong Fang

Doc ID: 276257 Received 03 Oct 2016; Accepted 08 Feb 2017; Posted 13 Feb 2017  View: PDF

Abstract: A set of bulk and fiber samples made of Tb3+ doped chalcogenide glass has been fabricated. For the fabricated samples the room temperature emission spectrum at 4.7 µm wavelength and the photoluminescence decay characteristics corresponding to the laser transition 7F5→7F6 were measured. These measurements confirm that the 7F4 transition is depopulated in a non-radiative way in Tb3+ doped selenide glass, which leads to the conclusion that terbium can be used for the realisation of a true 3-level system laser operating at the mid-infrared (MIR) wavelength of 4.7 µm. Further, FTIR (Fourier transform infrared spectroscopy) was used to measure the absorption cross-section spectrum. From measured absorption spectra the contribution of glass matrix impurity bands due to OH and Se-H were removed in order to perform Judd-Ofelt (J-O) analysis. The radiative transition rates calculated from J–O theory are compared with measured lifetimes. Using the experimentally extracted parameters, a numerical model of a Tb3+ doped fiber laser was developed. The model was used to analyze the dependence of the laser performance on the fiber length, output coupler reflectivity, pump wavelength, signal wavelength and fiber background loss. The modelling results show that an efficient 3-level mid-infrared fiber laser operating at 4.7 μm may be realised when pumping at a wavelength of either 2.013 μm or 2.95 μm.

Lattice modes and plasmonic linewidth engineering in gold and aluminum nanoparticle arrays

Davy Gerard, Dmitry Khlopin, Frédéric Laux, William Wardley, Jérôme Martin, Gregory Wurtz, Jerome Plain, Nicolas Bonod, Anatoly Zayats, and Wayne Dickson

Doc ID: 282987 Received 15 Dec 2016; Accepted 07 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: Lattice modes have been proposed as a means to engineer and control the linewidth and spectral position of optical resonances in arrays of metallic nanoparticles sustaining localized surface plasmon (LSP) resonances. Lattice modes are produced by the interference of LSP-enhanced in-plane scattered light, leading to a Fano-like lineshape with reduced linewidth. In this paper, we study the lattice modes supported by gold and aluminium nanoparticle arrays in the visible and UV, both experimentally and theoretically. The measured and simulated dispersion curves allow us to comprehensively analyze the details of the LSP coupling in the array. We show that when the spectral position of the Rayleigh anomaly, which depends on the period of the array, is slightly blue-shifted with respect to the LSP resonance, the quality factor in the nanoparticle array is significantly increased. We also provide evidence that the formation for the lattice modes, i.e. the coupling between LSPs and the in-plane scattered light, critically depends on the incident light polarization, the coupling efficiency being maximum when the polarization direction is perpendicular to the propagation direction of the grazing wave. The results obtained provide design rules allowing high quality factor resonances throughout visible and ultraviolet spectral ranges, needed for sensing and active nanophotonic applications.

Enhanced second harmonic generation and photon drag effect in a doped graphene placed on a two-dimensional diffraction grating

Tetsuyuki Ochiai

Doc ID: 283677 Received 27 Dec 2016; Accepted 07 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: We theoretically investigate the second harmonic generation and photon drag effect induced by an incident plane wave to a doped graphene placed on a two-dimensional diffraction grating. The relevant nonlinear conductivity of the graphene is obtained with a semi-classical treatment with a phenomenological relaxation. The grating acts not only as a plasmon coupler but also as a dispersion modulator of the graphene plasmon. As a result, the second harmonic generation is strongly enhanced by exciting the graphene plasmon polariton of the first- and/or second-harmonic frequencies. The photon drag effect is also strongly enhanced by the excitation of the plasmon at the first-harmonic frequency. The DC current induced by the photon drag effect flows both forward and backward directions to the incident light, depending on the modulated plasmon mode concerned.

Limits of coherent supercontinuum generation in normal dispersion fibers

Alexander Heidt, Jonathan Price, and James Feehan

Doc ID: 279960 Received 04 Nov 2016; Accepted 07 Feb 2017; Posted 09 Feb 2017  View: PDF

Abstract: We study the largely unexplored transition between coherent and noise-seeded incoherent continuum generation in all-normal dispersion (ANDi) fibers and show that highly coherent supercontinua with spectral bandwidths of one octave can be generated with long pump pulses of up to 1.5 ps duration, corresponding to soliton orders of up to 600 and an approximately 50 times increase of the coherent regime compared to pumping in the anomalous dispersion region. In the transition region we observe the manifestation of nonlinear phenomena that we term "incoherent cloud formation" and "incoherent optical wave breaking", which lead to a gradual or instantaneous coherence collapse of SC spectral components, respectively. The role played by stimulated Raman scattering and parametric four-wave mixing during SC generation in ANDi fibers is shown to be more extensive than previously recognized: their nonlinear coupling contributes to the suppression of incoherent dynamics at short pump pulse durations, while it is responsible for non-phase-matched parametric amplification of noise observed in the long pulse regime. We further discuss the dependence of SC coherence on fiber design, and present basic experimental verifications for our findings using single-shot detection of SC spectra generated by picosecond pulses. This work outlines both the further potential as well as the limitations of broadband coherent light source development for applications such as metrology, nonlinear imaging, and ultrafast photonics, amongst others.

The effect of feedback control on the dynamics of quantum discord with and without the rotating-wave approximation

Jing-Bo Xu, Jun-Qing Cheng, and Wei Wu

Doc ID: 279642 Received 28 Oct 2016; Accepted 06 Feb 2017; Posted 07 Feb 2017  View: PDF

Abstract: We investigate the effect of quantum-jump-based feedback on the dynamics of quantum discord for two non-interacting two-level atoms coupled to a single-mode of the cavity field with and without the rotating-wave approximation. It is found that the counter-rotating terms can be helpful for generating steady states and the value of steady-state quantum discord can be increased to approach 1 in the long-time limit by feedback controls. Furthermore, we also explore the influence of the time evolutions of mean excitation number in total system and atomic subsystem on the quantum correlations and show that the enhancement of mean excitation number in atomic subsystem by feedback controls leads to the high value of steady-state quantum discord.

Optics of multiple ultrasharp grooves in metal

Enok Skjølstrup and Thomas Sondergaard

Doc ID: 284438 Received 13 Jan 2017; Accepted 06 Feb 2017; Posted 07 Feb 2017  View: PDF

Abstract: The optics of multiple ultrasharp sub-wavelength grooves in metal is studied theoretically. Focus is on the transition from a single groove, where the scattering cross section is significant and can exceed the groove width, to infinitely many grooves in a periodic array with very low reflectance. When the multiple-groove array is illuminated by a plane wave the out-of-plane scattering is found to be extraordinarily large compared with the expected maximum from a geometric-optics estimate even for array widths of many wavelengths. The out-of-plane scattering is even higher per groove compared to the single-groove case. This is explained as an effect of surface-plasmon polaritons (SPPs) generated at one groove being scattered out of the plane by other grooves. This is supported by studies of the transmittance, reflectance, and out-of-plane scattering, when an SPP is incident on multiple grooves. When illuminating instead with a Gaussian beam, and observing the limit where the beam is confined well within the multiple-groove array, the total reflectance is very low and practically no scattering occurs.

Manipulation of entanglement sudden death in an all-optical experimental set-up

Urbasi Sinha, Siva Pradyumna, ASHUTOSH SINGH, and A. Ravi Rau

Doc ID: 275196 Received 02 Sep 2016; Accepted 06 Feb 2017; Posted 07 Feb 2017  View: PDF

Abstract: The unavoidable and irreversible interaction between an entangled quantum system and its environment causes decoherence of the individual qubits as well as degradation of the entanglement between them. Entanglement sudden death (ESD) is the phenomenon wherein disentanglement happens in finite time even when individual qubits decohere only asymptotically in time due to noise. Prolonging the entanglement is essential for the practical realization of entanglement-based quantum information and computation protocols. For this purpose, the local NOT operation in the computational basis on one or both qubits has been proposed. Here, we formulate an all-optical experimental set-up involving such NOT operations such that it can hasten, delay, or completely avert ESD, all depending on when it is applied during the process of decoherence. Analytical expressions for these are derived in terms of parameters of the initial state's density matrix, whether for pure or mixed entangled states. After a discussion of the schematics of the experiment, the problem is theoretically analyzed, and simulation results of such manipulations of ESD are presented.

Characterization of thresholdless point in PT symmetry electronic dimers

Fernande Fotsa-Ngaffo, Stephane Boris Tabeu, SENGHOR TAGOUEGNI, and Aurélien Kenfack-Jiotsa

Doc ID: 278836 Received 17 Oct 2016; Accepted 04 Feb 2017; Posted 07 Feb 2017  View: PDF

Abstract: A general model of electronic parity time symmetry (PTS) dimer is investigated. The system consists of a pair of an active LRC circuit, one with gain and another one with an equal amount of loss coupled by an inductance L, a capacitance C and a mutual inductance M. We successfully derive the breaking conditions and we show that the electronic PTS dimers resulting in coupling either with M, L or ML can be made thresholdless by adding a parallel coupling capacitance C. We also determine sufficient conditions for thresholdless transition and analyze scattering properties of the PTS dimers when inserted in a Hermitian transmission line. Interestingly, the linear PTS dimers prove the ability to control prohibited waves. In the region of real frequencies propagation, unidirectional invisibility is observed from the gain and loss incidence indicating a PTS scattering structure in both directions. Remarkably, when the coupling parameter in the transmission line exceeds a critical value, this unidirectionality is totally suppressed for the ongoing waves impinging upon the gain cell resulting in the absence of PTS property. Interestingly, lasing mode occurs in PTS dimers for real values of gain/loss modulation with real and complex wave numbers. However, when a dimer admits a threshodless transition, lasing mode will be additionally induced by imaginaries values of wave numbers inherent from real or purely imaginary values of the gain/loss modulation. These properties offer alternatives ways of designing novel linear optoelectronics devices.

Ultrathin conductive coating tailoring on the magnetic and electric resonances of silicon nanoparticles

Tian Feng, Jin Xiang, chengyun zhang, zixian liang, and Yi Xu

Doc ID: 281767 Received 30 Nov 2016; Accepted 04 Feb 2017; Posted 07 Feb 2017  View: PDF

Abstract: We reveal that the electric and magnetic resonances of silicon nanoparticles can be tailored by an ultrathin electric conductive coating layer which is usually involved in the conventional scanning electron microscope (SEM) characterization. By utilizing three typical electric conductive coatings, including gold (Au), platinum (Pt), and graphite (C), we show that the electric dipole resonance of the silicon nanoparticle will be broadened while the strength of magnetic resonances will be significantly reduced. In particular, we find that the unidirectional Fano resonant scattering occurs when a 9 nm Au coating is applied as well as the nearly annihilation of magnetic dipole resonance with only 9 nm Pt or C coating. It is therefore revealed that silicon nanoparticles would not properly work at their designed optical properties after such a pre-coating for SEM characterization. Our results might be helpful to bridge the gap between theoretical and experimental results in the study of resonant dielectric nanostructure and provide a strategy to engineer the optical properties of silicon nanoparticles.

Asymmetrically engineered metallic nanodisk clusters for plasmonic Fano resonance generation

Khai Le, Khang Nguyen, Phuc Toan Dang, and Khai Quang

Doc ID: 282852 Received 15 Dec 2016; Accepted 04 Feb 2017; Posted 07 Feb 2017  View: PDF

Abstract: In this paper, we numerically introduce a planar metamolecule that generates plasmonic Fano resonance. The engineered molecule consists of closely packed asymmetric gold nanodisks deposited on a glass substrate operating in the visible and near-infrared wavelengths. The asymmetric arrangement of nanodisks plays a key role in the Fano resonance generation. The induced extinction cross-section spectroscopy has a Fano-like shape owing to interference between bright and dark plasmonic modes sustained by the asymmetric nanodisk clusters. The Fano dips are shown to be highly sensitive to the inter-disk gaps as well as to the surrounding environment. As a result, we introduce a potential refractive index nanosensor having sensitivity (S) of 660 nm/RIU and figure of merit (FOM) of 4.75. The proposed metamolecule could be potential for various applications such as Fano-induced enhancement of solar energy harvesting, molecular fluorescence and photo up-conversion.

Dynamical Casimir effect of phonon excitation in the dispersive regime of cavity optomechanics

M H Naderi, ali motazedifard, and Rasoul Roknizadeh

Doc ID: 281821 Received 29 Nov 2016; Accepted 02 Feb 2017; Posted 03 Feb 2017  View: PDF

Abstract: In this paper, we theoretically propose and investigate a feasible experimental scheme for realizing the dynamical Casimir effect (DCE) of phonons in an optomechanical setup formed by a ground-state precooled mechanical oscillator (MO) inside a Fabry-P{\'e}rot cavity, which is driven by an amplitude-modulated classical laser field in the dispersive (far-detuned) regime. The time modulation of the driving field leads to the parametric amplification of the mechanical vacuum fluctuations of the MO, which results in the generation of Casimir phonons over time scales longer than the cavity lifetime. We show that the generated phonons exhibit quadrature squeezing, bunching effect, and super-Poissonian statistics which are controllable by the externally modulated laser pump. In particular, we find that the scheme allows for a perfect squeezing transfer from one mechanical quadrature to another when the laser frequency is varied from red detuning to blue detuning. Moreover, by analyzing the effect of the thermal noise of the MO environment, we find that there exists a critical temperature above which there is no phonon quadrature squeezing to occur. We also show that in the presence of time modulation of the driving laser the linewidth narrowing of the displacement spectrum of the MO can be considered as a signature of the generation of Casimir phonons.

Surface-Plasmon Excitation of Second-Harmonic light: Emission and Absorption

Maria Antonietta Vincenti, Domenico de Ceglia, Costantino De Angelis, and Michael Scalora

Doc ID: 283822 Received 30 Dec 2016; Accepted 01 Feb 2017; Posted 02 Feb 2017  View: PDF

Abstract: We aim to clarify the role that absorption plays in nonlinear optical processes in a variety of metallic nanostructures, and show how it relates to emission and conversion efficiency. We define a figure of merit that establishes the structure’s ability to either favor or impede second-harmonic generation. Our findings suggest that, despite the best efforts embarked upon to enhance local fields and light-coupling via plasmon excitation, nearly always the absorbed harmonic energy far surpasses the harmonic energy emitted in the far-field. Qualitative and quantitative understanding of absorption processes is crucial in the evaluation of practical designs of plasmonic nanostructures for the purpose of frequency mixing.

On optical tunneling in near-field diffraction of light from a small hole

Jesper Jung and Ole Keller

Doc ID: 279462 Received 25 Oct 2016; Accepted 31 Jan 2017; Posted 02 Feb 2017  View: PDF

Abstract: A quantitative theory describing optical tunneling effects relatedto near-field diffraction of light from a small hole in a flatscreen is established. Starting from a Green function reformulationof the microscopic Maxwell-Lorentz equations, which enables one toestablish separate integral expressions for the transverse (T) andlongitudinal (L) electric field's relation to the prevailing screencurrent density, we show, that in the absence of local-fieldcorrections, optical tunneling (i.e. the possibility of detectingphotons in front of the 'light cone') in near-field diffraction oflight from a small hole appears solely via the longitudinal Greentensor, $\mathbf{G}_\text{L}$, and the space-like part of theretarded transverse propagator,$\mathbf{G}_\text{T}^{\text{space}}$, both given in an appropriatecontraction scheme. It is demonstrated that$\mathbf{G}_\text{T}^{\text{space}}$ in the space-time domain can bewritten as a product of an electrostatic point-dipole tensor and atime factor which obeys microcausality and is nonvanishing only infront of a plane 'light cone'. The $\mathbf{G}_\text{L}$-tensor,which only exists in the space-frequency domain, also has theelectrostatic point-dipole tensor form around its singular point.Special attention is devoted to an analysis of the tunneling of anelectromagnetic pulse of finite duration through a small hole in anthin screen. In this particular case the tunneling signal in thepoint of observation arises from a somewhat complicated interplaybetween the time interval in which the effective aperture currentdensity is nonvanishing and the times it takes for the elementarytrailing edges of the individual space-like wavelets to pass theobservation point. To achieve a self-consistent description of thetunneling process in diffraction we propose to use a certainspatially nonlocal and linear constitutive equation to eliminate thescreen current density in favor of the prevailing transverseelectric field inside the screen. In this constitutive equation,which is an improved version of those used up to now in diffractiontheory, only the transverse part of the electric field occursbecause the induced longitudinal field is not a dynamical variablein electrodynamics. The formal solution of the resulting loopequation for the self-consistent transverse electric field isexpressed as a function of the transverse incident electric fieldassociated to the assumed far-field excitation of the chargedparticles of the screen. Lastly, we suggest to measure the opticaltunneling related to small hole diffraction via a modifiedfrustrated total internal reflection (FTIR)-tunneling experiment,and we indicate how it might be possible to extent the presenttheory to single-photon diffraction tunneling.

Enhanced sensitivity and measurement range SOI microring resonator with integrated one dimensional photonic crystal

Konstantinas Vaskevicius, Martynas Gabalis, Darius Urbonas, Armandas Balcytis, Raimondas Petruskevicius, and Saulius Juodkazis

Doc ID: 280096 Received 03 Nov 2016; Accepted 24 Jan 2017; Posted 26 Jan 2017  View: PDF

Abstract: We present a Silicon-on-Insulator microring resonator based refractive index sensor with enhanced sensitivity and measurement range. Both improvements are achieved by integrating one dimensional photonic crystal inside the microring waveguide. A photonic crystal is formed by periodically patterning, partially etching the rectangular perforations. Sensor performance is numerically analyzed for various combinations of perforation depth and length, each of which maintain a constant resonance wavelength. Our findings show that while deeper perforations result in a larger bulk refractive index sensitivity, the optimal design exhibiting the smallest limit of detection can be obtained at some intermediate value, depending on the leading term in sensor resolution. In addition to theoretical analysis, we present an experimental demonstration of a fabricated microring resonator with 120 nm height perforations.

Stabilization of class-B broad-area lasers emission by external optical injection

Anton Pakhomov, Rostislav Arkhipov, and Nonna Molevich

Doc ID: 280754 Received 15 Nov 2016; Accepted 11 Jan 2017; Posted 25 Jan 2017  View: PDF

Abstract: We theoretically examine the effect of external optical injection on the spatio-temporal dynamics of class-B broad-area lasers. We demonstrate that optical injection can efficiently stabilize the intrinsic transverse instabilities in such lasers associated with both the boundaries of the pumping area and with the bulk nonlinearities of the active medium. Stabilizing action of optical injection is shown to be closely related to the suppression of inherent relaxation oscillations behavior.

Modulation instability induced by higher-order nonlinear dispersions in nonlinear positive-negative index couplers with exponential saturable nonlinearity

Mohamadou Alidou, Aboukar NO LAST NAME GIVEN, and Alim Dia

Doc ID: 264583 Received 04 May 2016; Accepted 04 Oct 2016; Posted 04 Oct 2016  View: PDF

Abstract: We study the modulational instability (MI) in positive-negative couplers with higher-order effects and exponential saturable nonlinearity. Special attention is paid tothe influence of self-steepening (SS); intrapulse Raman scattering and second-order nonlinear dispersion (SOND) on the MI gain. The results show that saturable nonlinearity can be used to control the generation of sidebands through the coupler. We show that in normal dispersion regime, the instability gain exists even if theperturbation frequency ($\Omega$) is zero. The instability gain at $\Omega=0$ is nil, when the dispersion is anomalous. We find that the magnitude and sign of SOND exert strong influences on MI sideband. Moreover, by adjusting the various parameters such as SS, intrapulse Raman scattering, and SOND we obtain new instability regions.These results can be helpful to understand the generation of soliton-like exitaction in nonlinear oppositely coupler and can be potentially useful for future experiments.

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