带空气狭缝倒置结构的脊型硫系光波导后向受激布里渊散射研究

受激布里渊散射效应具有光谱线宽窄、频率稳定和增益方向敏感等优点,常用于激光器,慢光产生和微波光子滤波器等.本文基于As₂S₃硫系玻璃、以SiO₂为衬底设计了一种亚微米尺寸的带空气狭缝倒置结构脊型波导结构,具有高达8.22×10⁴ W^–1·m^–1的后向受激布里渊散射增益系数.研究显示在该结构的同种光学和声学模式下,更小的声光场有效模场面积具有更高的后向受激布里渊散射增益系数.还分析了硫系玻璃的光学损耗对后向受激布里渊散射的影响,发现当波导长度超过最优值后,斯托克斯光波功率开始下降,而增大泵浦光功率不仅可以提高斯托克斯光波功率的极大值,同时还会增大波导长度的最优值.当所输入的泵浦光功率为20 mW时,受激布里渊散射增益达到100 d B波导长度仅需要2 cm,这非常有利于光子器件的片上集成.     

基于色散调制的硒化砷条型波导的超连续谱产生

研究了基于色散调制硒化砷条型波导超连续谱的产生,通过调整波导结构参数,使零色散点转移到通信波长附近,在1.55μm波长处获得反常色散。波导长度为10 mm,波导横截面面积为500 nm×800nm,获得1.55μm波长处的非线性系数为48.754W^-1·m^-1。利用脉宽为579fs、重复频率为50 MHz、峰值功率为70 W的光纤激光脉冲在波导中产生了带宽600 nm的超连续谱。研究结果提供了一种使用常见激光泵浦平面波导实现集成片上超连续光源的途径。     

一种利用混合介质测量SBS介质布里渊线宽的方法

提出了一种利用双池受激布里渊散射(SBS)系统选用混合介质,进而测量SBS介质布里渊线宽的方法.在紧凑双池SBS系统的放大池中放入待测介质,在振荡池中放入布里渊频移可调的混合介质,测出放大池待测介质增益系数随布里渊频移偏离的洛伦兹曲线,该曲线半高处的线宽即为待测介质的布里渊线宽.实验上在Nd:YAG调Q激光系统中,选用CCl₄/C₆H₆混合介质,测量了四氯乙烯(C₂Cl₄)、六氯丁二烯(C_{关键词： 受激布里渊散射 混合介质 布里渊线宽}     

中红外高双折射高非线性宽带正常色散As2 S3光子晶体光纤

设计了一种中红外As₂S₃光子晶体光纤,利用多极法研究了这种光纤的双折射、色散和非线性特性.数值研究发现,该光纤在中红外波段λ = 3.625 μm处双折射B高达0.098;其x偏振方向的非线性系数γ_x达到了1.69 m^-1 ·W^-1, y偏振方向的非线性系数γ_y达到了0.78 m^{- 关键词： 光子晶体光纤 中红外波段 双折射 非线性}     

混合介质的SBS参数随混合比变化的研究

从混合介质的折射率、黏度、密度和声速等物理量随混合比的变化关系入手,推导出了混合介质的布里渊线宽、声子寿命和增益系数等受激布里渊散射(SBS)参数随混合比的变化关系.数值模拟了HT-70/FC-72混合介质的布里渊线宽、声子寿命和增益系数随FC-72体积分数的变化关系,并测定了该混合介质的吸收系数和光学击穿阈值随FC-72体积分数的变化关系.结果表明,HT-70/FC-72混合介质的SBS参数随FC-72体积分数单调变化,不出现极值现象.混合介质的选用不仅增加了SBS介质的种类,而且能够满足SBS系统对不 关键词： 受激布里渊散射 混合介质 SBS参数     

用负温度高能离子束的相对论多普勒效应实现从红外到X射线连续调谐激光器

利用负温度高能离子束的相对论多普勒效应,可能实现从红外到X射线连续调谐激光器。调谐范围△ν_T=2ν₀βγ。离子束从零到c调速时,激光频率为0—∞。本文给出了激光参数的相对论变换式,计算了负温度相对论离子束激光器的增益、阈值和输出特性,提出了用激光束对相对论离子束进行共振激发的方法,并讨论了He⁺离子束及Ar⁺离子束激光器的设计参数。 关键词：     

变温条件下受激布里渊散射增益系数的实验测量

从理论及实验上分析了介质温度对受激布里渊散射(stimulated Brillouin scattering, SBS)阈值及增益系数的影响.在理论分析的基础上, 提出了一种通过测量SBS阈值来决定介质SBS增益系数的新方法. 实验及测量结果表明, SBS增益系数会随着介质温度的增加而呈现指数上升的趋势. 关键词： 受激布里渊散射 阈值 增益系数     

脉冲CO2激光器的多频动力学模型

建立了适用于各种气压下(20×133—20×10⁵ Pa)的脉冲CO₂激光器的六温度多频动力学模型，该模型考虑了增益谱线重叠效应，序列带、热带的影响，以及非洛伦兹线型效应.对模型进行数值求解可以预言和解释不同气压下的脉冲CO₂激光器的输出特性，有助于评价不同的抽运设计和研究可调谐特性，为设计脉冲CO₂激光系统提供理论支持. 关键词： 2激光器')" href="#">CO₂激光器 激光动力学 六温度模型 增益谱线重叠     

受激布里渊散射新介质——全氟胺的研究

本文从介质化学结构与受激布里渊散射(SBS)特性的关系入手,寻找出了SBS特性良好的全氟胺系列新介质——FC-131,FC-3283,FC-40,FC-43,FC-70等,并测定或计算出了新介质的SBS参数. 结果表明,新介质的吸收系数均小于10^-3 cm^-1,光学击穿阈值均高于100 GW/cm². 全氟胺系列新介质不仅具有良好的SBS特性,而且还具有无毒、低挥发性和高稳定性等一系列独特的物理化学性质. 新介质的发现不仅增加SBS介质的种类,而且能够有效提高SBS系统的性能,对于SBS相位共轭镜在高功率激光系统中的应用打下了良好的基础. 关键词： 受激布里渊散射(SBS) 全氟胺 吸收系数 光学击穿阈值     

声波导单模光纤中后向受激布里渊散射的声模分析

本文推导了单模光纤中的声波亥姆霍兹方程,利用分离变量法求解并获得正规声波导导模的特征方程,定义了声模的归一化频率,结合贝塞尔函数的宗量近似分析了声波模式的特征值范围、截止频率和远离截止,探讨了声模的色散和布里渊增益谱的多峰成因.研究结果表明单模光纤中纵向声波基模L₀₁模无截止,主要被限制在纤芯中,与光基模耦合形成布里渊增益谱的主峰;高阶声模都存在低频截止,在包层分布比基模多,与LP₀₁模耦合形成布里渊增益谱的次峰.只有纵向L_0n声模对后向布里渊增益谱有贡献,纤芯掺锗浓度增大能使布里渊增益谱发生红移,声模数量增多, L₀₁模的增益峰值逐渐变大而高阶模的贡献减小.泵浦波长为1.55μm,纤芯掺锗浓度3.65%、纤芯半径4.2μm的单模光纤存在4个L_0n和16个Lmn (m>0)声模,声模L₀₁, L₀₃,L₀₄与光模LP₀₁声光耦合产生布里渊增益谱的1个主峰和2个弱峰;纤芯掺锗浓度15%,...     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.