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Nonlinear frequency combs generated by cnoidal waves in microring resonators

Zhen Qi, Giuseppe D'Aguanno, and Curtis Menyuk

Doc ID: 283615 Received 26 Dec 2016; Accepted 21 Feb 2017; Posted 21 Feb 2017  View: PDF

Abstract: Cnoidal waves are the periodic analogue of solitons. Like solitons, they can be generated in microresonators and correspond to frequency combs. The generation of frequency combs in nonlinear microresonators is governed by the Lugiato-Lefever equation. In this paper, we study the Lugiato-Lefever equation for a microresonator in the anomalous dispersion regime. In the lossless case, we show that the cnoidal waves can be expressed as a combination of Jacobi elliptic functions. These solutions reduce to known soliton-like solutions in particular cases. The properties of cnoidal waves in the realistic lossy case and their potential uses are also discussed.

Three-dimensional localized Airy elegant Laguerre-Gaussian light bullets in free space

Jiafan Wu, Fuqiang Huang, Yuqi Chen, Lang Cheng, Lefeng Li, and Dongmei Deng

Doc ID: 281672 Received 30 Nov 2016; Accepted 20 Feb 2017; Posted 21 Feb 2017  View: PDF

Abstract: By solving the (3+1)-dimensional ((3+1)D) free-space Schrödinger equation of an optical field analytically, we have demonstrated the 3-dimensional (3D) controllable Airy elegant Laguerre-Gaussian wave packets (AiELG), even mode AiELG wave packets and odd mode AiELG wave packets in free space. The AiELG wave packets are constructed by the Airy pulses with an initial velocity in temporal domain and the elegant Laguerre-Gaussian (elegant LG) beams in space domain. Furthermore, we demonstrate the numerical experiments of the elegant LG beams to study their evolution properties. Finally, we draw a conclusion that the evolution properties of the light bullets are influenced by the initial velocity, the evolution distance, and the mode numbers.

Optical waveguiding by necklace and azimuthon beams in nonlinear media

Lyubomir Stoyanov, Nikolay Dimitrov, Alexander Dreischuh, Dragomir Neshev, and Ivan Stefanov

Doc ID: 282046 Received 01 Dec 2016; Accepted 20 Feb 2017; Posted 21 Feb 2017  View: PDF

Abstract: Nonlinear necklace and azimuthon beams were experimentally generated in a self-focusing bulk photorefractive nonlinear medium (crystal SBN:60) using a frequency-doubled Nd:YVO4 laser at 532nm. The parallel optical waveguides induced by such a beam were probed by near-infrared signal beams emitted by a Ti:Sapphire laser. The quality and the time stability of the guided sub-beams at the exit of the crystal were investigated. In view of the waveguides’ ordering along a ring the best matching probe beams were found to be a singly- or a doubly-charged optical vortex bright rings. The results indicate the feasibility of parallel all-optical guiding of optical signals at wavelengths, for which the nonlinear medium is not photosensitive.

Topological properties of nearly flat bands in two-dimensional photonic crystals

Bing Yang, Tong Wu, and Xiangdong Zhang

Doc ID: 283657 Received 27 Dec 2016; Accepted 20 Feb 2017; Posted 24 Feb 2017  View: PDF

Abstract: Based on exact numerical calculations and physical analyses, we have demonstrated that there are two types of flat band in two-dimensional (2D) magnetic photonic crystals (PhCs). One has trivial topology with zero Chern number and the other has non-trivial topology with nonzero Chern number. The former originates from resonant scatterings of single scatters or cavity modes encircled by scatters in PhCs with complex lattices, while the latter comes from strong coupling interactions of fields among neighboring unit cells. Two types of flat band exhibit very different topological properties. When a point source with the frequency corresponding to the trivial flat band is placed inside the PhCs, its radiation is easily cloaked by metal obstacles. In contrast, non-trivial flat band states can bypass the obstacles.

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.

Optical sampling analog-to-digital converter based on two asynchronous mode-locked fiber lasers

Hongling Meng, Jianxiao Leng, Cheng Qian, and Jy Zhao

Doc ID: 277943 Received 30 Sep 2016; Accepted 15 Feb 2017; Posted 23 Feb 2017  View: PDF

Abstract: Using mode-locked fiber laser in electronic analog-to-digital converter (ADC) system has attracted more attention because optical pulse train generated by optical mode-locked fiber laser has ultrashort pulse width and ultralow timing jitter compared with electronic pulse train. Optical sampling ADC system based on mode-locked fiber laser makes great progress in high speed microwave signal ADC with high resolution. In this paper, we report an optical sampling ADC system based on two mode-locked fiber lasers with a slight difference in repletion frequency. With this scheme, we can digitize large wide band microwave signal based on optical pulse trains from two passive mode-locked fiber lasers with low repetition rate. We can measure carrier frequency precisely with subsampling method. In our system, the repetition rate of one mode-locked fiber laser is 100MHz and the other is (100M+1k) Hz. We digitize microwave signal at 10GHz with higher than 7 effective-number-of-bit (ENOB) resolution.

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.

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.

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.

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.

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.

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.

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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