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nonlinear effects in topological materials

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Frontiers of Optoelectronics 2021年第1期14卷 99-109页

作者： Jack WZUBER Chao ZHANG School of Physics University of WollongongNew South Wales 2522Australia

Materials,where charge carriers have a linear energy dispersion,usually exhibit a strong nonlinear optical response in the absence of disorder *** nonlinear response is particularly interesting in the terahertz frequency *** present a theoretical and numerical investigation of charge transport and nonlinear effects,such as the high harmonic generation in topological materials including Weyl semimetals(WSMs)and α-T_(3)*** nonlinear optical conductivity is calculated both semi-classically using the velocity operator and quantum mechanically using the density *** show that the nonlinear response is strongly dependent on temperature and topological parameters,such as the Weyl point(WP)separation b and Berry phase ФB.A finite spectral gap opening can further modify the nonlinear *** certain parameters,universal behaviors of both the linear and nonlinear response can be *** with experimentally accessible critical field values of 10^(4)-10^(5) V=m,our results provide useful information on developing nonlinear optoelectronic devices based on topological materials.

关键词： terahertz nonlinear effects topological materials Weyl semimetals(WSMs) α-T_(3) systems

Review of fiber superluminescent pulse amplifications

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High Power Laser Science and Engineering 2016年第3期4卷 106-112页

作者： Haitao Zhang Xinglai Shen He Hao Qinghua Li Mali Gong Center for Photonics and Electronics State Key Laboratory of Precision Measurement and Instruments Department of Precision Instruments Tsinghua University

High coherence of the laser is indispensable light sources in modern long or short-distance imaging systems, because the high coherence leads to coherent artifacts such as speckle that corrupt image formation. To deliver low coherence pulses in fiber amplifiers, we utilize the superluminescent pulsed light with broad bandwidth, nonlongitudinal mode structure and chaotic mode phase as the seed source of the cascaded fiber amplifiers. The influence of fiber superluminescent pulse amplification(SPA) on the limitations of the performance is analyzed. A review of our research results for SPA in the fibers are present, including the nonlinear theories of this low coherent light sources, i.e., self-focusing(SF), stimulated Raman scattering(SRS) and self-phase modulation(SPM) effects, and the experiment results of the nanosecond pulses with peak power as high as 4.8 MW and pulse energy as much as 55 mJ. To improve the brightness of SPA light in the future work, we introduce our novel evaluation term and a more reasonable criterion, which is denoted by a new parameter of brightness factor for active large mode area fiber designs. A core-doped active large pitch fiber with a core diameter of 190 μm and a mode-field diameter of 180 μm is designed by this method. The designed fiber allows near diffracted limited beam quality operation, and it can achieve 100 mJ pulse energy and 540 W average power by analyzing the mode coupling effects induced by heat.

关键词： superluminescent pulse amplification fiber amplification incoherent nonlinear effects very large mode field

Utilizing phase-shifted long-period fiber grating to suppress spectral broadening of a high-power fiber MOPA laser system

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High Power Laser Science and Engineering 2021年第3期9卷 33-39页

作者： Yinxu Bian Kerong Jiao Xuecheng Wu Hua Shen Feiyan Yang Rihong Zhu School of Electronic Engineering and Optoelectronic Technology Nanjing University of Science and TechnologyNanjing 210094China MIIT Key Laboratory of Advanced Solid Laser Nanjing University of Science and TechnologyNanjing 210094China Department of Material Science and Engineering University of California Los AngelesLos AngelesCA 90095USA

Suppressing nonlinear effects in high-power fiber lasers based on fiber gratings has become a *** present,research is mainly focused on suppressing stimulated Raman scattering in a high-power fiber ***,the suppression of spectral broadening,caused by self-phase modulation or four-wave mixing,is still a challenging attribute to the close distance between the broadened laser and signal *** using a traditional fiber grating with only one stopband to suppress the spectral broadening,the signal power will be stripped *** this challenge,we propose a novel method based on phase-shifted long-period fiber grating(PS-LPFG)to suppress spectral broadening in a high-power fiber master oscillator power amplifier(MOPA)laser system in this paper.A PS-LPFG is designed and fabricated on 10/130 passive fiber utilizing a point-by-point scanning *** resonant wavelength of the fabricated PS-LPFG is 1080 nm,the full width at half maximum of the passband is 5.48 nm,and stopband extinction exceeds 90%.To evaluate the performance of the PS-LPFG,the grating is inserted into the seed of a kilowattlevel continuous-wave MOPA *** results show that the 30 dB linewidth of the output spectrum is narrowed by approximately 37.97%,providing an effective and flexible way for optimizing the output linewidth of highpower fiber MOPA laser systems.

关键词： fiber optics component high-power fiber laser nonlinear effects phase-shifted long-period fiber grating spectral broadening

Practical evaluation of the drag of a ship for design and optimization

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Journal of Hydrodynamics 2013年第5期25卷 645-654页

作者： YANG Chi HUANG Fuxin NOBLESSE Francis Center for Computational Fluid DynamicsGeorge Mason University State Key Laboratory of Ocean Engineering and School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong University

We consider two major components of the drag of a ship, the ＂friction drag＂ and the ＂wave drag＂, that are related to viscous friction at the hull surface and wavemaking, and mostly depend on the Reynolds number and the Froude number, respectively. We also consider the influence of sinkage and trim, viscosity, and nonlinearities on the drag. The sum of the friction drag given by the classical ITTC friction formula and the wave drag predicted by the modification, called Neumann-Michell （NM） theory, of the classical Neumann-Kelvin theory of ship waves is found to be within about 10% of experimental drag measurements for four ship hulls for which theoretical predictions and experimental measurements are compared. The sum of the ITTC friction drag and the NM wave drag can then be expected to yield realistic practical estimates that can be useful for routine applications to design and hull- form optimization of a broad range of displacement ships. Furthermore, we note several simple extensions of this highly simplified approach that can be expected to significantly improve accuracy.

关键词： friction drag wave drag Neumann-Michell (NM) theory sinkage and trim nonlinear effects

Influence of medium parameters on power limiting characteristic in stimulated Brillouin scattering process

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Chinese Optics Letters 2007年第11期5卷 674-676页

作者：龚华平吕志伟林殿阳刘松江 Institute of Opto-Electronics Harbin Institute of Technology Harbin 150001 Institute of Opto-ElectronicsChina Jiliang UniversityHangzhou 310018 Institute of Opto-Electronics Harbin Institute of Technology Harbin 150001 Institute of Opto-Electronics Harbin Institute of Technology Harbin 150001 Department of PhysicsDaqing Petroleum InstituteDaqing 163318

By adopting noise initiation model of stimulated Brillouin scattering （SBS）, the influence of phonon lifetime and gain coefficient of medium on power limiting characteristic is numerically investigated. Through using actual parameters of three media, CCl4, acetone, and CS2, the waveforms of transmitted pulses are simulated. The result shows that different media have little effect on the front peak of waveform, while have an obvious effect on the height of power limiting platform. When the medium which has short phonon lifetime and small gain coefficient is used, the height of power limiting platform is comparatively high. In experiment, by focusing 1064-nm, 8-ns, 18-mJ pulses into these three media, the waveforms of transmitted pulses are obtained. The experimental results are in good agreement with conclusions of theoretical simulations.

关键词： Brillouin scattering High power lasers nonlinear effects Optical limiting Stimulated Brillouin scattering Stimulated scattering

Generation of modified duobinary return-to-zero format using polarization-maintaining fiber loop mirror

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Chinese Optics Letters 2007年第2期5卷 69-70页

作者：王欣张新亮 Wuhan National Laboratory for Optoelectronics & Institute of Optoelectronics Science and Engineering Huazhong University of Science and Technology Wuhan 430074

Modified duobinary return-to-zero （MD-RZ） format is an improvement of optical duobinary （ODB） *** paper proposes a novel, all-optical method to generate-MD-RZ format by using a polarization main-talning fiber loop mirror （PMFLM）. Operation principle for all-optical format conversion is theoretically analyzed and the output spectrum is simulated. 40-Gb/s MD-RZ data format generation is experimentally demonstrated.

关键词： Cross phase modulation Modulators nonlinear effects Polarization maintaining fibers Self phase modulation Signal processing

Self-organized voids revisited:Experimental verification of the formation mechanism

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Chinese Physics B 2014年第7期23卷 732-737页

作者：宋娟叶俊毅钱梦迪骆芳芳林贤卞华栋戴晔马国宏陈庆希姜燕赵全忠邱建荣 School of Material Science and Engineering Jiangsu University Physics Department Shanghai University State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Key Laboratory of Specially Functional Materials of Ministry of Education and Institute of Optical Communication Materials South China University of Technology

We conduct several experiments to further clarify the formation mechanism of a self-organized void array induced by a single laser beam, including energy-related experiments, refractive-index-contrast-related experiments, depth-related ex- periments, and effective-numerical-aperture experiment. These experiments indicate that the interface spherical aberration is indeed responsible for the formation of void arrays.

关键词： void array interface spherical aberration nonlinear effects

Facile synthesis of aqueous silver nanoparticles and silver/molybdenum disulfide nanocomposites and investigation of their nonlinear optical properties

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Tungsten 2021年第4期3卷 482-491页

作者： Xiao-Yan Zhang Hong-Qiang Wang Yi Sun Wei Zhou Jun Wang Department of Chemistry Shanghai UniversityShanghai 200444China Laboratory of Micro-Nano Photonic and Optoelectronic Materials and Devices Key Laboratory of Materials for High-Power LaserShanghai Institute of Optics and Fine Mechanics(SIOM)Chinese Academy of Sciences(CAS)Shanghai 201800China Center of Materials Science and Optoelectronic Engineering University of Chinese Academy of SciencesBeijing 100049China Shanghai Aerospace Hydrogen Energy Technology Co. LtdShanghai 201108China State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics(SIOM)Chinese Academy of Sciences(CAS)Shanghai 201800China

Silver nanoparticle (AgNP) aqueous colloids with different surface plasmon resonance (SPR) frequencies were controllably synthesized by a facile and green chemical synthesis method. The obtained AgNPs with an average diameter of ~ 15 nm show a symmetrical SPR peak at ~ 400 nm. Another longitudinal SPR mode at ~ 520 nm occurs when increasing the amount of ethanol according to the ultraviolet-visible light spectra. The third-order nonlinear optical (NLO) absorption properties of the AgNP colloids were found to switch from two-photon absorption (TPA) to saturable absorption (SA) by tuning the SPR frequency using Z-scan technique with 340 fs pulses at 515 nm. When combined with two-dimensional (2D) MoS_(2), an enhanced SA response is observed for Ag/MoS_(2 )nanocomposites compared with the counterparts. The nonlinear absorption coefficient of Ag/MoS_(2) nanocomposites is about − (10.93 ± 0.6) × 10^(-2 )cm·GW^(−1), which is almost three times higher than that of MoS_(2). Our work has an instructive value in promoting the potential application of AgNPs and its nanocomposites in optoelectronic and photonic devices, such as optical limiting and ultrafast laser pulse generation.

关键词： Silver nanoparticles Two-dimensional molybdenum disulfide Chemical synthesis nonlinear effects Optical properties

UltraJam:Ultrasonic adaptive jammer based on nonlinearity effect of microphone circuits

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高置信计算(英文) 2023年第3期3卷 30-39页

作者： Zhicheng Han Jun Ma Chao Xu Guoming Zhang School of Computer Qinghai Normal UniversityXining 810008China Department of Computer Science UC DavisDavis 95616USA School of Computer Science and Technology Shandong UniversityQingdao 266237China

The widely used devices(***,recorders)equipped with microphones have posed a severe threat to confidential *** this paper,we design an inaudible anti-eavesdropping method:UltraJam,to reduce the risk of unwanted and secret *** uses the ultrasonic signal to mask *** leveraging the nonlinear effect of microphone circuits,the adaptive ultrasonic signal can be recorded and demodulated into low-frequency which can effectively squash the *** on the characteristics of the attenuation coefficient and frequency response,we construct a number of jamming signals with different bandwidths and designed a wideband signal injection array,meanwhile adaptively adjust the power at each bandwidth signal to cover more frequency bands and increase usage *** verify the security of the microphone jamming system,we also utilize several audio recovery methods to recover the raw signal from jamming *** experimental results show that less than 1% of the words are recognized in the jamming recording,and even with the audio recovery method,99% of the words still cannot be recognized in the recovered jamming recording.

关键词： Noise jammer Microphone nonlinear effects Security