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Near resonant nanosecond laser-driven nonlinear optical response in As <sub/>50</sub> S <sub/>50</sub> thin films
摘要： Nanosecond near resonant excitation in As50S50 thin films leads to strong nonlinear optical response, i.e. nonlinear absorption coefficient up to 4 × 106 cm GW?1 and nonlinear refractive index of 8.5 cm2 GW?1, both of which are the strongest ever reported in amorphous semiconductors. We propose a three-level energy band model to explain this effect, which indicates that the nonlinear process is reverse saturable absorption in nature, mediated by excited-state absorption from slow interband transition between the conduction and valence band. On the other hand, observation of negative nonlinear refractive index reveals the occurrence of self-defocusing effect. Finally, benefitting from the strong nonlinear response, we demonstrate a promising application of As50S50 thin films as an optical limiter for optoelectronic sensors.
关键词： chalcogenide,nonlinear optics,Z-scan,thin films
更新于2025-09-19 17:13:59
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Cm-Level Photonic-Crystal-Like Subwavelength Waveguide Platform with High Integration Density
摘要： In this paper, the cm-level photonic-crystal-like subwavelength waveguide platform is developed and analyzed by using the finite-difference time-domain method. The configuration can be considered as a hybrid waveguide combining with the advantages of a metal-dielectric-metal waveguide and a photonic crystal waveguide. The symmetric and high reflection effect of metallic sidewall and the effect of the photonic crystal structure on the light-guiding mechanism and integration characteristics of the waveguide are systematically investigated. The results reveal that the cm-level photonic-crystal-like waveguide platform provides subwavelength confinement and very low propagation loss with the isolation more than 30 dB, which are promising for high-density photonic integration. The tradeoff between integration density and propagation loss is optimized. In addition, a T-shaped power splitter based on the waveguide platform is proposed. The excess loss of the T-shaped power splitter is less than 0.4 dB. A set of passive components can be exploited on the proposed cm-level photonic-crystal-like subwavelength waveguide platform in future work to constitute the large-scale integrated photonic systems.
关键词： integrated optics,photonic crystals,waveguide splitter,subwavelength waveguides
更新于2025-09-19 17:13:59
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[IEEE 2018 International Conference on Intelligent Computing and Communication for Smart World (I2C2SW) - Erode, India (2018.12.14-2018.12.15)] 2018 International Conference on Intelligent Computing and Communication for Smart World (I2C2SW) - An Improved Transformerless Inverter Topology for Grid Connected Photovoltaic System
摘要： In this paper, we report on an optical tolerance analysis of the submillimeter atmospheric multi-beam limb sounder, STEAMR. Physical optics and ray-tracing methods were used to quantify and separate errors in beam pointing and distortion due to re?ector misalignment and primary re?ector surface deformations. Simulations were performed concurrently with the manufacturing of a multi-beam demonstrator of the relay optical system which shapes and images the beams to their corresponding receiver feed horns. Results from Monte Carlo simulations show that the inserts used for re?ector mounting should be positioned with an overall accuracy better than 100 m ( 1/10 wavelength). Analyses of primary re?ector surface deformations show that a deviation of magnitude 100 m can be tolerable before deployment, whereas the corresponding variations should be less than 30 m during operation. The most sensitive optical elements in terms of misalignments are found near the focal plane. This localized sensitivity is attributed to the off-axis nature of the beams at this location. Post-assembly mechanical measurements of the re?ectors in the demonstrator show that alignment better than 50 m could be obtained.
关键词： Stratosphere–Troposphere Exchange And climate Monitor Radiometer (STEAMR),submillimeter-wave instruments,quasi-optics,multi-beam,tolerance analysis,Monte Carlo,Limb viewing
更新于2025-09-19 17:13:59
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Nonlinear energy deposition of filamentation with femtosecond Airy laser beams in water
摘要： The nonlinear propagation of femtosecond Airy laser ?laments in water is numerically investigated in this paper. We mainly consider the in?uences of con?nement parameter, pulse duration and beam waist on the deposited energy of ?laments. The values of con?nement parameter are found to have a signi?cant impact on the temporal and spatial dynamics of the pulse. The characteristics of energy deposition also di?er widely for Airy beams with di?erent con?nement parameters. The less the con?nement parameter, the more energy deposited by ?lamentation. However, the relative deposited energy evolves relatively small changes under di?erent con?nement parameters. We also found the longer pulse duration and longer beam waist are bene?cial to the total deposited energy increase.
关键词： self-focusing,Airy beams,energy deposition,Ultrafast nonlinear optics
更新于2025-09-19 17:13:59
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Raman scattering and self-steepening in nonlinear plasmonic waveguide pulse equation
摘要： In this paper, we use Maxwell equations and the first order perturbation theory to obtain pulse propagation equation in a plasmonic waveguide made of nonlinear dielectric material. In this study, the effects of nonlinear self-steepening and Raman scattering are considered. Nonlinear coefficients of phase modulation, Raman and self-steepening are calculated numerically in terms of frequency and compared with a standard silica fiber. Obtained values of the nonlinear coefficients are about up to 300 times larger than that of standard silica optical fibers. So they can be used as part of all optical integrated circuit such as continuum generation, optical switching and frequency conversion.
关键词： Nonlinear optics,Self-steepening,Raman scattering,Nonlinear plasmonic waveguide
更新于2025-09-19 17:13:59
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An Alternative Approach for High Uniformity Distribution of Indoor Lighting LED
摘要： A high accurately theoretical analysis for high uniformity illumination distribution on the ceiling of indoor lighting LED system based on the super-positions is proposed and performed. Starting from the non-uniform illumination distribution of two LED sources, the dependences of the uniformity ratio on the height of the LED source and the length of the ceiling are investigated. The low intensity in the region near the side-wall can be avoided by rotating the LED source with a small angle, but the low uniformity illumination distribution at the center of the ceiling still exists. The aim of this work proposes the alternative design and approach for several con?gurations and demonstrates that can be obtained high uniform illumination distribution. The redistributed factor of the illumination through the lens is also considered and calculated. The investigation of this work will be a general guideline for designing the high uniform LED indoor lighting systems as well as being valuable materials for the LED lighting manufacturing industry.
关键词： freeform optics,LED lighting,indoor lighting system
更新于2025-09-19 17:13:59
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4-dB Quadrature Squeezing With Fiber-Coupled PPLN Ridge Waveguide Module
摘要： We have developed an optical parametric amplification module for quadrature squeezing with input and output ports coupled with optical fibers for both fundamental and second harmonic. The module consists of a periodically poled LiNbO3 ridge waveguide fabricated with dry etching, dichroic beamsplitters, lenses and four optical fiber pigtales. The high durability of the waveguide and the good separation of squeezed light from a pump beam by the dichroic beamsplitter enable us to inject intense continuous-wave pump light with the power of over 300 mW. We perform ?4.0±0.1 dB of noise reduction for a vacuum state at 1553.3 nm by using a fiber-optics-based measurement setup, which consists of a fiber-optic beamsplitter and a homemade fiber-receptacle balanced detector. The intrinsic loss of the squeezed vacuum in the module is estimated to be 25%. Excluding the extrinsic loss of the measuremental system, the squeezing level in the output fiber of the module is estimated to be ?5.7±0.1 dB. A modularized alignment-free fiber-coupled quadrature squeezer could help to realize quantum information processing with fiber optics.
关键词： PPLN waveguide,fiber optics,squeezed light
更新于2025-09-19 17:13:59
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[IEEE 2020 IEEE/SICE International Symposium on System Integration (SII) - Honolulu, HI, USA (2020.1.12-2020.1.15)] 2020 IEEE/SICE International Symposium on System Integration (SII) - Calibration of Laser Optics for Sensor Guided Remote Cutting
摘要： In the last several years, laser based material processing has established itself in many industrial branches as an economical manufacturing process. Laser remote cutting in particular is widespread in the automotive sector. In order to take full advantage of laser remote cutting, it is necessary to position the laser beam precisely on the workpiece using a handling kinematic system. Therefore, this work focuses on the combination of standard industrial robots with laser scanner optics. To address this configuration, this paper proposes a method for the calibration of the parameters, which describe the precise position of the 3D laser scanner optics in respect to the robot. Moreover, the robot introduces a new source of deviation, which is then compensated by using an external measuring system to guide the scanner optics during processing.
关键词： thermography,remote laser scanner optics,machining,calibration,automation,digital image processing
更新于2025-09-19 17:13:59
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Numerical approaches for solving the nonlinear Schr??dinger equation in the nonlinear fiber optics formalism
摘要： This work presents a novel numerical stability analysis of a collection of pseudo-spectral methods, also known as split-step methods, for solving pulse propagation modelled by the nonlinear Schr¨odinger equation in the nonlinear ?ber optics formalism. In order to guarantee the convergence of di?erent pulse propagation dynamics, the numerical solutions of the pseudo-spectral methods (split-step Fourier method, symmetric split-step Fourier method, fourth order Runge-Kutta in the interaction picture method, and an optimization of split-step Fourier schemes for pulse propagation over long distances) are tested by the validation of the conservation laws that govern this system. The presented numerical results are an illustrative guide to consider in the selection of an appropriate numerical method in future investigations of a wide variety of propagation problems that involve the interplay of the linear and nonlinear contribution in the nonlinear Schr¨odinger equation, in order to reproduce accurately a speci?c phenomenology using this formalism.
关键词： nonlinear ?ber optics,Nonlinear Schr¨odinger equation,split-step methods,optical ?ber,optical pulse propagation
更新于2025-09-19 17:13:59
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[OSA Optical Fiber Communication Conference - San Diego, California (2019..-..)] Optical Fiber Communication Conference (OFC) 2019 - Energy Consumption Modelling of Coherent Transmission in Data Centers
摘要： We analyze energy consumption of coherent transmitters and receivers for intra- and inter-data center links and model trends in energy consumption of global-scale data center networks as the volume of traffic increases. OCIS codes: (060.1660) Coherent communications; (060.2360) Fiber optics links and subsystems
关键词： Fiber optics links and subsystems,Coherent communications
更新于2025-09-19 17:13:59