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Accepted papers to appear in an upcoming issue

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Channeling the dielectric breakdown of air by a sequence of laser-generated plasma filaments

Pavel Polynkin, Zhanna Samsonova, Andreas Schmitt-Sody, Jennifer Elle, audrian lucero, and Alexander Englesbe

Doc ID: 371236 Received 03 Jul 2019; Accepted 17 Sep 2019; Posted 18 Sep 2019  View: PDF

Abstract: We have investigated channeling the DC dielectric breakdown of a 20 cm air gap by a sequence of four concatenated plasma filaments, independently produced by four focused, 5 picosecond-long laser pulses. The polarity of the applied DC voltage, as well as the temporal delay between the four pulses was varied from few to 400 nanoseconds, in the attempt to find the optimum direction and speed of the stepping filament sequence. We have found that the filament sequence reliably channeled the breakdown and measurably reduced the breakdown threshold voltage, relative to that in the unguided breakdown. However, no meaningful dependence on either the polarity of the applied DC voltage or the stepping speed of the filament sequence was observed. Our results support the established scenario of channeling the DC air breakdown by laser filaments, which is primarily based on the creation of a reduced-density air channel bridging the discharge gap. The channeling mechanism associated with seeding the discharge leader by the filament plasma plays a negligible role.

Quantum heat engine with a quadratically coupled optomechanical system

Muhammad Naseem and Ozgur Mustecaplioglu

Doc ID: 373030 Received 18 Jul 2019; Accepted 17 Sep 2019; Posted 18 Sep 2019  View: PDF

Abstract: We propose a quantum heat engine based on a quadratically coupled optomechanical system. The optical component of the system is driven periodically with an incoherent thermal drive, which induces periodic oscillations in the mechanical component. Under the action of the quadratic optomechanical interaction, the mechanical mode evolves from an initial thermal state to a thermal-squeezed steady-state, as verified by calculating the Wigner functions. The dynamics of the system is identified as aneffective four-stroke Otto cycle. We investigated the performance of the engine by evaluating the dissipated power, the maximum power under a load, and the maximum extractable work. It is found that the engine operating with quadratic optomechanics is more powerful than the oneoperating with linear optomechanics. The effect is explained by the presence of squeezing in the quantum state of the mechanical mode.

Femtosecond pulse delivery around 1560 nm in large core inhibited coupling fibers

Dominik Dobrakowski, Anupamaa Rampur, Grzegorz Stepniewski, Dariusz Pysz, Luming Zhao, Yuriy Stepanenko, Ryszard Buczynski, and Mariusz Klimczak

Doc ID: 372842 Received 17 Jul 2019; Accepted 16 Sep 2019; Posted 16 Sep 2019  View: PDF

Abstract: Transmission of ultrashort laser pulses under 100 fs at a central wavelength of 1560 nm from a mode-locked laser is investigated over meter-scale lengths of an inhibited-coupling fiber with 65 µm core diameter. Performance of the fiber in this application is evaluated experimentally using cross-correlation frequency-resolved optical gating, either with the fiber loosely coiled up to 3 m of length or bent over one full loop down to 6 cm radius. Experimental results on observed dispersive stretching of the pulse up to around 200 fs are compared with nonlinear propagation simulations using GNLSE parametrized with measured characteristics of the fiber. Dechirping of the pulse to its original shape in the fiber under bending is observed and related to suppression of higher order modes. We show, that the proposed fiber can be used to transmit around 90 fs long laser pulses without spectral or temporal distortions, if a 6 cm radius loop is applied.

A high-loss and broadband photonic crystal fiber polarization filter with two large apertures coated with gold layers

Xin Yan, Yuanhongliu Gao, Tonglei Cheng, and Shuguang Li

Doc ID: 374749 Received 06 Aug 2019; Accepted 15 Sep 2019; Posted 18 Sep 2019  View: PDF

Abstract: A high-loss and broadband photonic crystal fiber (PCF) polarization filter based on the surface plasma resonance is designed. The designed filter has two large symmetrical holes coated with a metal film. The characteristics of the polarization filter are calculated by the finite element method(FEM).Two pairs of holes near the core are used to obtain high loss. Gold plating in the air holes is used to generate the resonance, which converts a part of the light energy into free-electron vibration energy. The fiber parameters are optimized to achieve specific functions. The proposed filter structure achieves a loss value of 3261.7 dB/cm in the y-direction at 1.31μm, while the loss in the x-direction is very small, and the loss peaks in the x- and y-direction are obviously separated. The thickness of a metal layer and the arrangement and size of air holes near the core are discussed; also, the optimal structure regarding the characteristics of metal-filled polarization filters in photonic crystal fibers is obtained. To the best of our knowledge, this is the first report on a polarization filter than can achieve a loss of up to 3000 dB/cm.

High-amplitude dissipative solitons in the normal and anomalous dispersion regimes

Sofia Latas and Mario F.S. Ferreira

Doc ID: 374418 Received 01 Aug 2019; Accepted 15 Sep 2019; Posted 16 Sep 2019  View: PDF

Abstract: In this work, the propagation of high-amplitude solitons of the cubic-quintic complex Ginzburg-Landau equation, both in the normal and anomalous dispersion regimes, has been studied. Using the method of moments, and starting from a singularity found by Akhmediev and co-workers, high-amplitude pulses were predicted in the normal and anomalous dispersion regimes. In general, numerical computations are in good agreement with the predictions based on that approximate method. The effect of the reactive quintic nonlinearity is also investigated.

Four-wave mixing of XUV pulses and IR pulses for studies of atomic dynamics

Khuong Dinh, Khoa Anh Tran, Peter Hannaford, and Lap Dao

Doc ID: 373075 Received 18 Jul 2019; Accepted 14 Sep 2019; Posted 16 Sep 2019  View: PDF

Abstract: We apply a cascaded four-wave mixing process in the extreme ultraviolet (XUV) region using two collinear multiple-cycle laser pulses with incommensurate frequencies (wavelengths 1400 and 800 nm) to construct a two-dimensional cross-correlation spectrum. We show that the two-dimensional spectrum can be used to extract the amplitude and phase modifications of the atomic dipole moments of the coupled states in atomic krypton interacting with the intense pulsed laser light. The experimental configuration and a simple model for qualitative interpretation allow us to demonstrate the validity and power of the 2D spectroscopy method in the XUV region.

Mode and lasing characteristics for scissor-FP hybrid-cavity semiconductor lasers

Ya-Qian Ye, Min Tang, yong-Heng zhang, Yue-De Yang, Jin-Long Xiao, and Yong-Zhen Huang

Doc ID: 373202 Received 19 Jul 2019; Accepted 14 Sep 2019; Posted 16 Sep 2019  View: PDF

Abstract: Hybrid-cavity semiconductor lasers consisting of a Fabry-Perot (FP) cavity with one side connected to a scissor-shaped microcavity are proposed and demonstrated to achieve lasing mode control. Single-mode lasing and dual-mode lasing can be achieved for the laser by adjusting the scissor-cavity and the FP-cavity injection currents. Dual-mode operation is experimentally verified with a mode interval varied from 8.06 to 11.01 nm by varying the scissor-cavity current, and agrees well with the mode simulation by finite element method, for a laser with the FP cavity length of 300 μm and the scissor microcavity of two deformed rings with radii of 15 and 8 μm. In addition, single-mode lasing with a side-mode suppression-ratio of 27 dB is achieved with a wavelength tuning from 1554.98 to 1559.84 nm by varying the scissor-cavity current.

Casimir force between two plasmonic metallic plates from a real frequency perspective

Hideo Iizuka and Shanhui Fan

Doc ID: 373973 Received 06 Aug 2019; Accepted 14 Sep 2019; Posted 16 Sep 2019  View: PDF

Abstract: We consider the Casimir force from a real frequency perspective, in a system consisting of two plasmonic metallic plates separated by a vacuum gap, in order to elucidate the connection between the Casimir force behavior and the underlying electromagnetic modes. This system supports a set of discrete modes including gap plasmon modes and guided modes. Previous works have shown that the behavior of the Casimir force in this system is well explained by the gap plasmon modes when the vacuum gap has a size of a 10nm or less. We show that in the intermediate regime where the gap size is approximately 100nm, the contribution from the discrete modes, which are repulsive except for the lowest-order gap plasmon mode, is no longer sufficient to account for the behavior of the Casimir force. Instead, the contribution from a continuum spectrum, which is always attractive, plays a significant role. These two contributions, when integrated over the frequency, can be comparable in magnitude in the intermediate gap size regime. Our results show that including the contribution from the continuum spectrum is essential in understanding the attractive nature of the Casimir interaction. We further show that in a low-loss material system, the contributions of the discrete modes exhibit a resonant Lorentzian lineshape, and the peak resonance amplitude is proportional to the inverse of the resonance linewidth at each resonance, leading to the fact that the Casimir force is independent of the damping rate of a material.

Influence of spatial dispersion on surface plasmons, nanoparticles and grating couplers

Armel Pitelet, Nikolai schmitt, Dimitrios Loukrezis, claire scheid, Herbert De Gersem, Cristian Ciracì, emmanuel centeno, and Antoine Moreau

Doc ID: 368168 Received 21 May 2019; Accepted 12 Sep 2019; Posted 13 Sep 2019  View: PDF

Abstract: Recent experiments have shown that spatial dispersion may have a conspicuous impact on the response of plasmonic structures. This suggests that in some cases the Drude model should be replaced by more advanced descriptions that take spatial dispersion into account, like the hydrodynamic model. Here we show that nonlocality in the metallic response affects surface plasmons propagating at the interface between a metal and a dielectric with high permittivity. As a direct consequence, any nanoparticle with a radius larger than 20 nm can be expected to be sensitive to spatial dispersion whatever its size. The same behavior is expected for a simple metallic grating allowing the excitation of surface plasmons, just as in Wood’s famous experiment. Finally, we carefully set up a procedure to measure the signature of spatial dispersion precisely, leading the way for future experiments. Importantly, our work suggests that for any plasmonic structure in a high permittivity dielectric, nonlocality should be taken into account.

Optimal condition for optical trapping of large particles: tuning the laser power and numerical aperture of the objective

Nader Reihani and hossein gorjizadeh

Doc ID: 368823 Received 31 May 2019; Accepted 12 Sep 2019; Posted 13 Sep 2019  View: PDF

Abstract: A Gaussian laser beam tightly focused through a high numerical aperture objective lens, so-called Optical tweezers, is widely used for pico-newton range force spectroscopy. Utilizing a proper values for parame- ters such as bead size, numerical aperture of the objective, power of the laser is always a challenge. Here we show which set of the values for the parameters can maximize the lateral trapping efficiency. Our re- sults show that for a high numerical aperture force spectroscopy a bead with a diameter of 4-5μm would be suitable, and that for manipulation using large beads utilizing a proper values for laser power and nu- merical aperture of the objective would be crucial. We present a practical method for choosing the power of the laser that maximizes the lateral trapping efficiency.

Photon avalanche effect in quantum wells: controlling light with light

Aleksei Popov, Andrei Ivanov, and Evgeniy Perlin

Doc ID: 370954 Received 25 Jun 2019; Accepted 12 Sep 2019; Posted 13 Sep 2019  View: PDF

Abstract: A mechanism of controlling the absorption of high-intensity light with the frequency ω and the intensity jω by complementary light with the frequency Ω > 2ω and the two or three orders of magnitude lower intensity jΩ is proposed. The mechanism is based on the photon avalanche effect in quantum wells. The electron concentrations in size quantization subbands and conduction band continuum and the absorbed power of light with the frequency ω are obtained as functions of the intensities jω and jΩ and the time of exposure to laser radiation t. It is established that the resulting dependences exhibit well-pronounced threshold behavior. For example, at jΩ ~ 0.2¬1 kW/cm² and t ~ 0.1¬5 ns, it is possible to control the absorption of high-intensity light ω, so that the absorption of light Ω is practically lacking at intensities jω below the threshold intensity (40¬200 kW/cm²) and becomes very strong at intensities above the threshold intensity. The case when light Ω is the third harmonic of high-intensity light ω is also considered.

Tunable plasmon-induced transparency absorbers based on few-layer black phosphorus ribbon metamaterials

Chao Liu, Hongjian Li, Hui Xu, Mingzhuo Zhao, Cuixiu Xiong, Baihui Zhang, and Kuan Wu

Doc ID: 373534 Received 23 Jul 2019; Accepted 12 Sep 2019; Posted 13 Sep 2019  View: PDF

Abstract: Black phosphorus is a newfangled plasmonic material at the infrared region. We have achieved a mid-infrared plasmon-induced transparency absorption phenomenon via the excitation of black phosphorus surface plasmon using a symmetrical raised ribbon structure. The absorption efficiency can be greatly improved by adding a gold mirror at the bottom of the structure. The relative Fermi level can effectively adjust the absorption efficiency and wavelength. The symmetrical protrusions and ribbon connect to each other and it is beneficial to the operation of the relative Fermi level. After that, the influence of the size of the symmetrical protrusions on absorption characteristics is researched. The results show that the absorption efficiency of the two absorption peaks reaches up to 75%. The angular dependence of the two orientations of the material is used to compare the anisotropy of black phosphorus. This structure can be implemented to realize a mid-infrared modulator, switch controller and absorption device with two prominent functions.

Tunable and Broadband Coherent Perfect Absorption by Ultrathin Black Phosphorus Metasurfaces

Tianjing Guo and Christos Argyropoulos

Doc ID: 370399 Received 18 Jun 2019; Accepted 11 Sep 2019; Posted 11 Sep 2019  View: PDF

Abstract: Black phosphorus (BP), a relative new plasmonic two-dimensional (2D) material, offers unique photonic and electronic properties. In this work, we propose a new tunable and broadband ultrathin coherent perfect absorber (CPA) device operating in the terahertz (THz) frequency range. It is based on a bifacial metasurface made of BP patch periodic arrays separated by a thin dielectric layer. Broadband CPA bandwidth is realized due to the ultrathin thickness of the proposed device and the extraordinary properties of BP. In addition, a substantial modulation between CPA and complete transparency is achieved by adjusting the phase difference between the two counter-propagating incident waves. The CPA performance can be tuned by dynamically changing the electron doping level of BP. The CPA response under normal and oblique transverse magnetic (TM) and electric (TE) polarized incident waves is investigated. It is derived that CPA can be achieved under both incident polarizations and across a broad range of incident angles. The presented CPA device can be used in the design of tunable planar THz modulators, all-optical switches, detectors, and signal processors.

Step-index fluoride fibers with all-normal dispersion for coherent mid-infrared supercontinuum generation

Yu Li, Longfei Wang, Meisong Liao, yinyao liu, Xia Li, wanjun bi, Fei Yu, Long Zhang, Yiguang Jiang, Wang Zaiyang, Longfei Zhang, Chengfeng Yuan, and Lili Hu

Doc ID: 372444 Received 11 Jul 2019; Accepted 10 Sep 2019; Posted 10 Sep 2019  View: PDF

Abstract: Step-index fluorozirconate (ZBLAN) and fluoroindate (InF3) fibers with all-normal dispersion (ANDi) are proposed for mid-infrared (MIR) nonlinear application. The fibers have flat and near-zero ANDi profile at MIR region to generate highly coherent MIR supercontinuum (SC). Multiwatt coherent MIR SC is allowed to guide in the ANDi ZBLAN and InF3 fibers of 5.5 μm and 6.5 μm core diameters. The MIR SC are simulated in the ANDi fluoride fibers pumped with high peak power at 1960 nm and 2700 nm. The simulation results show that highly coherent MIR SC spanning from 1100 to 3000 nm with flatness <10 dB generates from the ANDi ZBLAN fiber pumped at 1960 nm, and highly coherent MIR SC extending from 1500 nm to 3800 nm can generate from the ANDi InF3 pumped at 2700 nm. These ANDi step-index fluoride fibers are available and promising nonlinear mediums for achieving high power all-fiber structure coherent MIR SC source.

Quantum phase communication channels assisted by non-deterministic noiseless amplifiers

HAMZA ADNANE, Berihu Gebrehiwot, and Matteo Paris

Doc ID: 366296 Received 29 Apr 2019; Accepted 05 Sep 2019; Posted 10 Sep 2019  View: PDF

Abstract: We address quantum M-ary phase-shift keyed communication channels in the presence of phase diffusion, and analyze the use of probabilistic noiseless linear amplifiers (NLA) to enhance performance of coherent signals. We consider both static and dynamical phase diffusion and assess the performances of the channel for ideal and realistic phase receivers. Our results show that NLA employed at the stage of signal preparations is a useful resource, especially in the regime of weak signals. We also discuss the interplay between the use of NLA, and the memory effects occurring with dynamical noise, in determining the capacity of the channel. © 2019 Optical Society of America

Nonlinear absorption in media with composite gold nanoparticles

Alexander Iskandar, Anna Fitriana, and C. Martijn de Sterke

Doc ID: 368026 Received 20 May 2019; Accepted 05 Sep 2019; Posted 10 Sep 2019  View: PDF

Abstract: We consider nonlinear absorption in a system consisting of a dilute mixture of identical metallic nanoparticles in a dielectric background. The nanoparticles consist of a core and a shell, one of which is gold and the other is a dielectric. By determining their effective nonlinear parameters, we find that the nonlinear absorption can be positive or negative, depending on the filling fraction of the gold. This shows that the magnitude and sign of the effective parameters depend not only on the constituent materials, but also on the details of thegeometry.

Photothermal mirror Z-scan spectrometry

Aristides Marcano Olaizola

Doc ID: 372066 Received 08 Jul 2019; Accepted 04 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: This contribution introduces a pump-probe photothermal mirror Z-scan method to measure the thermal quantum yield, the thermal diffusivity, and other photothermal parameters of a solid. The focusing of a pump beam of light onto the sample generates thermo-elastic surfaces distortions. The distorted surface acts as a mirror affecting the diffraction pattern of a reflected probe beam yielding the experimental signal. Scanning the focusing lens produces a single peak photothermal mirror Z-scan signature. The amplitude and time evolution of the signal determine the sample’s photothermal properties. The method is used to analyze gallium arsenide and silicon plates, obtaining good agreement with previous studies.

Dual-polarized star gap nano-antenna

Monir Morshed, Lei Xu, and Haroldo Hattori

Doc ID: 374241 Received 30 Jul 2019; Accepted 03 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: Nano-antennas are being used in optical data storage, near-field imaging, photovoltaics, sensing and spectroscopy applications. In many cases, the antennas work with linear polarization, but some applications require circularly polarized light such as field-enhanced circular dichroism spectroscopy. Circular dichroism spectroscopy is a technique used to study organic molecules and is widely used in biology and medicine. In this article, we analyze a star gap nano-antenna array. The antenna combines circular gratings and a symmetric gap to provide maximum electric field enhancement factor of around 48 at 780nm with the average electric field enhancement factor of about 34.75 due to its geometry, the antenna can work for both linear and circularly polarized light, having similar electric field enhancement factors. Due to its symmetry and capacity to work with different polarizations, the antenna can find applications in sensing and spectroscopy. As an example of application, we have characterized the antenna for Surface Enhancement Raman spectroscopy (SERS) and obtained a SERS factor of4.18×106 for the 880cm−1 Raman line of ethanol.

ULTR-ABROADBAND ABSORBER BASED ON A FUNNEL-SHAPED ANISOTROPIC METAMATERIAL

Salah Obayya, Ghada ABDELATIF, Mohamed Hameed, and Mohamed Hussein

Doc ID: 369753 Received 11 Jun 2019; Accepted 03 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: A novel design of funnel-shaped anisotropic metamaterial absorber is reported with periodic array of nickel-germanium (Ni/Ge). The optical properties of the suggested anisotropic metamaterial absorber are numerically calculated using 3D finite difference time domain (FDTD) technique. Composed of both cylindrical and conical units, the reported anisotropic metamaterial attains high absorption over wavelength range from 200 nm to 9000 nm with an average absorption of 96%. A wide wavelength absorption band is achieved from ultraviolet to near-infrared including the visible range. The cylindrical unite could harvest low-order modes, while the longer wavelengths are trapped through the conical part. The enhanced broadband absorption is due to the excitation of multiples orders of slow-light modes. In addition, the effect of the incident angle on the absorption of transverse magnetic (TM) and transverse electric (TE) polarized waves are also investigated. Further, the structural geometrical parameters are studied in order to maximize the absorption through the proposed design.

Optomechanically induced transparency and Fano resonances in graphene based nanocavity

Sajid Qamar, Assad Hafiz, Zia uddin, and Muqadder Abbas

Doc ID: 363420 Received 26 Mar 2019; Accepted 03 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: We propose a theoretical model to obtain optomechanically induced transparency (OMIT) and Fano resonances in a nanocavity using graphene bilayer as intracavity medium. The motivation comes from an earlier work where Fano resonances have been reported using bilayer graphene [T.-T. Tang, \textit{et al}, Nature Nanotechnology, \textbf{5}, 32 (2010)]. We consider a similar bilayer graphene system, however, inside an optomechanical nanocavity and investigate the effects of different parameters on the output probe field. Here, one mirror of the nanocavity is considered coherently driven by the pump and probe fields whereas second mirror has mechanical oscillation due to the radiation pressure. We consider interaction of bilayer graphene with the optomechanical cavity and show that OMIT and Fano line shapes can be obtained corresponding to output probe field frequency. We notice that OMIT and two Fano resonances can be obtained by manipulated certain parameters, i.e., optomechanical interaction ($g_{mc}$), interaction of G-mode phonon and electronic state ($\lambda_k$), and the coupling between cavity and G-mode phonon ($g_{cp}$). Interestingly, the system exibits OMIT and Fano resonances simultaneously at different probe field frequencies. The accompanying dispersions are very steep and, therefore, extreme slow light can be achieved which can lead to realize optical storage devices and memories. We also notice that OMIT and Fano resonances are very sensitive to the interaction of cavity modes with the oscillating mirror ($g_{mc}$), therefore, due to this enhanced sensitivity, our proposed system can be used to increase the sensitivity of the interferometer \cite{{shi}}. Further, another advantage of using graphene is that it performs better as compared to metals in plasmonic devices.

Asymmetric Einstein-Podolsky-Rosen Steering Manipulating among Multipartite Entangled States

Zhai Shuqin, Nan Yuan, and Kui Liu

Doc ID: 368625 Received 31 May 2019; Accepted 03 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: Asymmetric Einstein-Podolsky-Rosen (EPR) steering means the ability of one party can nonlocally “steer” the state in other side through local measurements. The asymmetric property of Einstein-Podolsky-Rosen steering provides adequate security in one-sided device-independent secure quantum communication protocol. In this manuscript, we theoretically investigate the asymmetric EPR steering schemes between two subsystems of multipartite entangled states by asymmetric modulation method. Two schemes, including tripartite entangled state to bipartite steering and quadripartite entangled state to tripartite steering are investigated. By reconstructing the covariance matrix of a continuous variable (CV) multipartite Gaussian states, we quantify the steerability of manipulated two different subsystems, and demonstrate the EPR steering parameter versus various types states parameters. Our work provide a reference for asymmetric quantum information processing and enrich resource for secure quantum networks.

Enhanced third harmonic generation for s- and p- polarized optical surface modes of 1D photonic crystal structure.

V. Konopsky, Alexey Melnikov, Elena Alieva, and Sergey Chekalin

Doc ID: 369207 Received 03 Jun 2019; Accepted 03 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: Generation of the third harmonic radiation, visible to the naked eye as a collimated green beam, is obtained via femtosecond excitation of the optical surface modes (SMs) propagating along a one-dimensional (1D) photonic crystal (PC) for s- and p- polarization separately. For both polarizations, the PC SMs exist at the fundamental and third harmonic frequencies, that allows efficient nonlinear conversion at the phase-matching points. The pattern of the third harmonic surface wave scattering is detected and modeled, and it is shown that this pattern reveals the mode structure of the PC. Applications of the studied 1D PC structure for the experimental testing of 2D nonlinear materials are discussed.

Supercontinuum Generation in Seven-Core Fibers

Aku Antikainen and Govind Agrawal

Doc ID: 370837 Received 24 Jun 2019; Accepted 02 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: We present a detailed numerical study of supercontinuum generation in hexagonal seven-core fibers with single-core input. The key spectral broadening mechanisms are shown to result from or strongly depend on the frequency dependence of linear coupling between the cores. Soliton and supercontinuum behavior in seven-core fibers is demonstrated to support rich dynamics that can bear resemblance to single-mode fibers, graded-index or step-index multi-mode fibers, or none of these.

Online measurement of the optical aberrations of a thin-disk laser active medium using Fourier domain multiplexing method

Mohammad Reza Jafarfard, Mohammad Hossein Daemi, and Shahram Kazemi

Doc ID: 372275 Received 10 Jul 2019; Accepted 02 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: We present an interferometric scheme for the measurement of the deformation of a thin-disk laser active medium with visible light as the probe beam. The disk has a small wedge angle, and the coatings on its both sides have appreciable reflectance for visible light that prevents using a standard interferometric profilometry procedure. The method that can acquire data in a video rate is based on the interference of three beams, two beams reflected from both sides of the disk and one the reference beam of the interferometer. To obtain the phase variations caused by the deformation of the disk, a Fourier domain multiplexing method has been utilized. The optical setup was designed in a manner that these three beams be separated in Fourier domain. The measured data for different deformation profiles of the disk are well agreed with that of obtained with profilometry with an IR probe beam. This method is a fast and simple method since only a single shot in a CCD sensor is required to acquire the morphology of the active medium in thin-disk lasers.

Study of UV Rayleigh Scattering thermometry for flame temperature field measurement

Qianlong Wang, Liqiao Jiang, Weiwei Cai, and Yi Wu

Doc ID: 371591 Received 03 Jul 2019; Accepted 01 Sep 2019; Posted 04 Sep 2019  View: PDF

Abstract: This paper explores the Rayleigh scattering thermometry via a wavelength of 355 nm through a unique measurement scheme. In this context, the P-polarization and S-polarization Rayleigh scattering of flame and air (as the temperature calibration reference) are measured. Therefore, the subtraction of P-polarization Rayleigh scattering intensity from that of S-polarization is proposed to eliminate the background noise and fluorescence interference influence to reduce the temperature measurement uncertainties. As a result, the temperature field of CH4/N2/O2 premixed flame at φ=0.78 on McKenna burner is detected by this Rayleigh scattering thermometry and the axial temperature profile is validated with the literature data. Within the Region of Interest (ROI) domain (-5 to 5 mm in the radial direction), an overall temperature measurement uncertainties of ± 46.5 K is reported. Moreover, both the influence of P-polarization Rayleigh scattering and laser sheet in-homogeneity on the temperature measurement is further quantitatively studied. Furthermore, the measurement uncertainties relevant to laser energy variation and flame Rayleigh scattering cross-section variation due to temperature increase are specified as 1.4% and 2-8%, respectively. Eventually, temperature measurement of single-shot images are attempted and the large signal dynamic range (100-1000 [a.u.]) indicates the promising potential for the temperature field interpretation of turbulence combustion.

Numerical study on Kerr frequency comb generation in Si3N4 microresonators with frequency-dependent access coupler properties

Napoléon Gutierrez, arnaud fernandez, Olivier LLOPIS, Stephane Calvez, and Stéphane Balac

Doc ID: 370242 Received 25 Jun 2019; Accepted 31 Aug 2019; Posted 04 Sep 2019  View: PDF

Abstract: Within the frame of vertically coupled silicon nitride (Si3N4) resonators characterized with 220 GHz free spectral range driven by a continuous wave laser at 1.55 µm for Kerr comb generation, the design of achromatic critically coupled resonators may bring severe issues because of the difficulty in designing dispersion-free access couplers with controlled coupling factor over a large spectral bandwidth. As a consequence of this, numerical simulations of Kerr Frequency comb in these structures may drastically differ from reality if frequency-dependence of the access coupler’s properties is not taken into account in the simulated model. In order to address this issue, we have developed a numerical model that takes into account the frequency dependence of the access coupler coefficients and remains valid even for the simulation of low Q factor resonators. Field propagation within the ring is described by the nonlinear Schrödinger equation. Novelty in the model resides in the computation of a complex-valued, frequency dependent coupling transfer function between resonant ring and underlying access waveguide that models frequency-dependent dispersion and losses in the access coupling region of the resonator. Based on simulation results, we discuss on the differences observed in Kerr comb generation in resonators with three different coupler designs initially intended to yield critical coupling over the largest achievable bandwidth.

INPUT COUPLING ENHANCEMENT THROUGH ANTENNA INCORPORATION IN THIN AU-MICA TRENCH WAVEGUIDES

Isabel Pita, Mahendar Kumbham, Matthew Gleeson, SERGUEI BELOCHAPKINE, Kevin Ryan, Christophe Silien, and Ning Liu

Doc ID: 369383 Received 05 Jun 2019; Accepted 31 Aug 2019; Posted 04 Sep 2019  View: PDF

Abstract: The ability of both bowtie and semicircle antennas to enhance waveguide input coupling efficiency in thin trench waveguides was studied for broadband applications. The waveguide output of trench waveguides with and without antennas were measured using a tunable laser with wavelengths ranging from 570 nm to 900 nm under both parallel and perpendicular polarization conditions. The results indicated that the waveguides with antennas performed better than the trench waveguide alone for parallel polarization conditions with maximum enhancements of 51 and 32 from the simulations, and 14.4 and 5.2 experimentally for the bowtie and semicircle respectively. Conversely there was no significant enhancement for the perpendicular polarization. This was attributed to the excitation of either the gap mode, or the surface plasmon mode depending on polarization.

Exploiting the circular polarization of light to obtain a spiral energy flow at the subwavelength focus

Anton Nalimov, Victor Kotlyar, and Sergey Stafeev

Doc ID: 371851 Received 04 Jul 2019; Accepted 29 Aug 2019; Posted 30 Aug 2019  View: PDF

Abstract: Using Richards-Wolf formulas, we show analytically that when strongly focusing a circularly polarized axisymmetric non-vortex field (e.g., a Gaussian beam or zero-order Bessel-Gaussian beam), a spiral energy flow is produced around the subwavelength focal spot. This phenome-non can be explained by the conversion of spin angular momentum associated with the circu-lar polarization state into the near-focus orbital angular momentum, with the on-axis angular momentum being strictly zero. It is also shown that a linearly polarized optical vortex with topological charge +2 or -2 produces an on-axis near-focus energy backflow whose ampli-tude (defined by the negative longitudinal component of Poynting vector) is comparable with that of the incident beam.

Generation of ultrashort laser pulses through a resonant interaction of quasi-continuous wave packet with running refractive index wave

Marina Yavtushenko, Igor Zolotovskii, Dmitry Korobko, Andrei Fotiadi, Pavel Mironov, Dmitry Sementsov, and Victor Lapin

Doc ID: 370933 Received 24 Jun 2019; Accepted 28 Aug 2019; Posted 29 Aug 2019  View: PDF

Abstract: Modulation instability followed by generation of subpicosecond pulses could be obtained with quasicontinuous wave packets propagating in optical fibers with running refractive index wave. We report on comprehensive studies of this process demonstrating that the peak power of the pulses exceeds the power of the pumping radiation by orders of magnitude. Practically, the effect could be implemented through interaction of the surface optical wave with an acoustic wave in 2-cm cylindrical waveguide in a robust all-fiber format.

Manipulating giant cross-Kerr nonlinearity at multiple frequencies in an atomic gaseous medium

Bang Nguyen, Doai Le, An Nguyen, and Khoa Dinh

Doc ID: 367079 Received 09 May 2019; Accepted 27 Aug 2019; Posted 27 Aug 2019  View: PDF

Abstract: We proposed a model for manipulating giant cross-Kerr nonlinearity in an atomic gaseous medium consisting of six-level inverted-Y systems. The absorption, dispersion and cross-Kerr nonlinear coefficients of the medium are derived as analytical functions of the parameters of probe, coupling and signal fields. It is shown that the cross-Kerr nonlinearity is enhanced significantly in three transparent windows under electromagnetically induced transparency (EIT). Furthermore, the cross-Kerr nonlinearity can be manipulated between positive and negative values by controlling intensity and/or frequency of the coupling laser. Such controllable giant cross-Kerr nonlinearity with the analytical interpretation is convenient to find experimental parameters and it is useful for studying applications of controllable multi-channel quantum phase gates.

Optical rectification of ultrafast Yb-lasers: Pushing power and bandwidth of THz generation in GaP

Jakub Drs, Norbert Modsching, Clement Paradis, Christian Kraenkel, Valentin Wittwer, Olga Razskazovskaya, and Thomas Südmeyer

Doc ID: 369518 Received 10 Jun 2019; Accepted 27 Aug 2019; Posted 28 Aug 2019  View: PDF

Abstract: We demonstrate broadband high-power THz generation at MHz repetition rates by optical rectification in GaP driven by an ultrafast Yb-based thin-disk laser oscillator. We investigate the influence of pulse duration in the range of 50 fs to 220 fs and thickness of the GaP crystal on the THz generation. Optimization of these parameters with respect to the broadest spectral bandwidth yields a gap-less THz spectrum extending to nearly 7 THz. We further tailor the driving laser and the THz generation parameters for the highest average power, demonstrating 0.3 mW THz radiation with a spectrum extending to 5 THz. This was achieved using a 0.5 mm thick GaP crystal pumped with a 95 fs, 20 W thin disk laser, operating at 48 MHz repetition rate. We also provide a comprehensive method to estimate the THz spectrum, which can be used for design and optimization of similar THz systems.

Tunable Mid-Infrared Graphene-Titanium Nitride Plasmonic Absorber for Chemical Sensing Applications

Mehrnoosh Salemizadeh, Fatemeh Fouladi Mahani, and Arash Mokhtari

Doc ID: 371547 Received 03 Jul 2019; Accepted 23 Aug 2019; Posted 26 Aug 2019  View: PDF

Abstract: In this paper, using double-layer graphene nanograting arrays on top of a titanium nitride ground plane, a tunable plasmonic sensor has been presented for mid-infrared chemical sensing applications. Utilizing the plasmonic field enhancement and near-field coupling of the double-layer graphene scheme, narrowband absorption spectra in the mid infrared region have been achieved for the required selective characteristic of the proposed sensor. The large surface area and atomic level thickness of graphene result in high surface sensitivity leading to the tunability of the resonant wavelength of the sensor by the chemical potential variation. Moreover, employment of titanium nitride as the ground plane benefits from its abundance and low cost, fabrication stability, high melting point, and bio-compatibility compared to metallic plates. Using finite-difference time-domain numerical simulations, it has been shown that the proposed sensor yields high sensitivity and figure of merit of 3188.8 nm/RIU and 9.1 RIU-1, respectively in the refractive index range of 1.31 to1.39. To prove the feasibility of the design for chemical sensing applications, the sensor response in contact with organic aromatic pollutants in water has also been investigated demonstrating a high sensitivity of 29250 nm/RIU and figure of merit of 83.5 RIU-1.

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