布里渊散射线宽对边缘探测技术定标数据的影响

用边缘探测技术测量水中的布里渊散射信号,可以得到很高的测量精度.当布里渊散射线宽随海水温度、盐度的变化而改变时,探测到的信号强度也会随之发生变化,从而影响数据定标.在考虑布里渊散射线宽随温度变化的基础上,重新对用边缘探测方法测量水中布里渊散射信号所得的数据进行定标.实验中用一个偏振棱镜改变被测信号相对于两个吸收池布儒斯特窗的偏振状态,发现偏振状态的改变会导致定标数据变化.     

用碘分子共振吸收滤波器精确测量水中的布里渊散射频移

提出了一种基于分子共振吸收滤波技术的水中布里渊散射频移的探测方法——边缘探测方法。利用碘分子在水中的布里渊散射光谱范围内的两个对称的吸收峰,可以对光在水中的布里渊散射频移实现高精度的实时测量。对这一方法的原理进行了分析,给出了可用于实际测量的探测系统,并给出了用此系统得到的实验测量结果。还分析了测量系统的固有误差及测量灵敏度。结果表明,这一新方法与常规探测方法(如扫描干涉仪法)相比,具有实时性好、灵敏度高、测量精度高等突出的优点。     

布里渊散射及其在激光雷达中的应用

在简要介绍布里渊散射的基本性质的基础上,重点介绍了布里渊散射在激光雷达中的应用。主要分析了布里渊散射在水中声速测量、粘滞系数的测量和水中目标探测方面的原理和技术实现。     

水中受激布里渊散射阈值的研究

在对水中受激布里渊散射阈值的研究中,针对传统定义上的不足,提出一种新的定义和新的测量方法.测量了不同能量的光束在不同长度的水介质中传输,在宽线宽和窄线宽情况下水的衰减系数.通过水的衰减系数的变化来确定不同情况下受激布里渊散射的阈值.试验发现,水中的受激布里渊阈值在理想稳态和理想瞬态下是一个常数,只与泵浦激光和介质属性有关,和介质长度无关;在中间情况下,受激布里渊阈值是否与介质长度有关,还要根据具体情况来分析.     

水中微弱光散射布里渊频谱选择性光放大研究

提出利用布里渊放大技术对水中微弱光散射信号进行频谱选择性光放大的方法.根据频率失谐布里渊放大理论模型，分析了Stokes种子光的线宽及频率失谐对布里渊放大的影响，研究了种子光放大率随水温及其功率密度变化的规律，理论和实验符合较好.研究表明，相同频率失谐时，线宽较大的种子光信号放大率更高.选取20℃的CS₂为放大介质，不同温度海水产生的Stokes种子光信号均能得到有效的布里渊放大.相同抽运光功率密度情况下，种子光的放大率随其功率密度的增加而减小，当种子光能量约为5μJ时，其放大率达10²以上.     

水中受激布里渊散射脉冲的反常压缩

受激布里渊散射(SBS)具有脉冲压缩的特性,受激布里渊散射的脉冲宽度随着抽运能量的增大而变小,在水中可以达到几百皮秒的量级.本文在实验上观察到一种受激布里渊散射的脉冲宽度随抽运能量增大而变大的现象,这里称之为反常压缩.SBS的脉冲反常压缩和脉冲压缩与抽运光的强弱会聚情况有关.利用数值模拟,模拟了强弱会聚情况下抽运光在水中的传输规律,强弱会聚情况的抽运光对受激布里渊散射形成的有效增益长度不同:抽运光强会聚时有效增益长度短,形成SBS脉冲宽度的反常压缩;弱会聚时有效增益长度长,也就是正常的SBS脉冲压缩.     

受激布里渊散射对激光在水中衰减特性的影响

测量了不同能量的光束，通过不同长度的水介质在窄线宽与宽线宽两种情况下的衰减系数，研究了受激布里渊散射对激光在水中衰减特性的影响.结果发现，激光光束在水中传播时的衰减系数与激光光强和线宽有关，而不是通常情况下所认为的常数.还从理论上进行了分析.     

受激布里渊散射对激光在水中衰减特性的影响

测量了不同能量的光束,通过不同长度的水介质在窄线宽与宽线宽两种情况下的衰减系数,研究了受激布里渊散射对激光在水中衰减特性的影响.结果发现,激光光束在水中传播时的衰减系数与激光光强和线宽有关,而不是通常情况下所认为的常数.还从理论上进行了分析. 关键词： 衰减系数 受激布里渊散射     

基于激光布里渊散射的高速气流测试技术

激光布里渊散射是由介质密度涨落引起的一种非弹性散射现象,其散射谱特征参数（频移、线宽）取决于散射角和散射介质压强、温度等参数,通过探测高速气流激光布里渊散射谱,可反演获得高速气流压强、温度等参数。介绍了基于激光布里渊散射原理的高速气流参数测试原理,设计了一种基于法布里 珀罗干涉仪的高速气流参数测试装置,搭建实验平台获取了高速氮气气流的激光布里渊散射谱。实验结果表明,通过激光布里渊散射谱获得的高速气流压强、温度值与理论值相对误差在15%以内。     

基于布里渊散射信号检测的大气探测模型

以激光信号在传输介质中的布里渊散射频移量模型为基础,依据相关大气数据建立基于布里渊散射信号检测的大气探测模型。该模型中布里渊频移量只与大气高度相关,详细描述了低空大气范围内布里渊频移量的连续分布状态。结果表明在086 km的海拔高度范围内,大气的布里渊散射频移量分布在1.01.3 GHz之间。与有关数据相比,该模型与实际情况非常符合,同时具有很好的连续性和普适性。     

Analyzing statistical errors for measurements of Brillouin scattering by the edge technique

The signal estimate and statistical uncertainty in the measurements of Brillouin shift by the edge technique are analyzed in detail. A signal to noise parameter factor is introduced and is used to discuss the statistical uncertainty in the measurements. The effect of signal averaging and the effect due to background noise are analyzed. Some helpful conclusions are predicted. PACS 42.68.Wt; 42.79.Qx; 78.35.+c     

Method for measuring the threshold value of stimulated Brillouin scattering in water

A new method for accurate measurement of the threshold value of stimulated Brillouin scattering (SBS) in water in terms of pump laser intensity is investigated. The threshold value of SBS is determined by the point of the deviation of the value of the attenuation coefficients of wide- and narrow-linewidth lasers rather than the intensity of the backscattered SBS signal in the material.     

The edge technique as used in Brillouin lidar for remote sensing of the ocean

A new approach to remote sensing of the ocean is proposed. It is based on a combination of Brillouin scattering, incoherent lidar techniques and high-resolution frequency discrimination via gas absorption cells. The results of theoretical and experimental research are given. This approach provides the capability of rapid real-time monitoring of sound-speed or temperature profiles both in the open ocean and in littoral zones with high resolution and high accuracy. PACS 42.68.Wt; 42.79.Qx; 78.35.+c     

A new method for measuring the threshold of stimulated Brillouin scattering

A new method for measuring the threshold of stimulated Brillouin scattering (SBS) based on the generation location of a Stokes beam is proposed for the first time to our knowledge. The length of the medium cell is selected to be longer than the free gain length of pump pulses in the Brillouin medium. The reflected light from a certain mirror in front of the medium cell is chosen as the reference beam, and the SBS threshold is measured by the "jump" of the delay between the Stokes beam and the reference beam. An 8-ns Q-switched single-longitudinal-mode pulse is used as the pump and the typical SBS medium FC-72 is selected as the nonlinear medium in our experiment. The SBS threshold intensity is measured to be 173-178 mW/cm 2 , which is consistent with existing results measured with the transmitted energy limiting method.     

Resonant cancellation of Brillouin scattering at the indirect edge in GaP

The incident photon-energy dependence of the Brillouin-scattering intensity from acoustic waves injected into GaP is studied at room temperature in the photon-energy range 2.175–2.27 eV. It is found that the Brillouin-scattering cross-section resonantly cancels near the indirect absorption edge. The observed cancellation can be accounted for by the resonant contributions arising from the resonance between the incident photon-energy and the indirect-energy gap.     

Ultrasonic enhanced Brillouin light scattering in water

Brillouin light spectra in water was experimentally investigated by a scanning Fabry-Perot interferometer. The optical properties of the scattering media were modulated by a plane ultrasound wave. An enhancement up to 10 times of the Brillouin signal by modulation with the ultrasound wave has been seen clearly. The dependence of the Brillouin signal amplitude on the ultrasound frequency, amplitude and the position of the ultrasound field based to the light beam was investigated experimentally. Very strong dependence of the enhancement with experimental conditions was obtained.     

Calibration of edge technique considering variation of Brillouin line width at different temperatures of water

Edge technique is a sensitive and accurate technique for measuring Brillouin shift in water. Calibration is necessary in its applications in remote sensing of the ocean. In previous works, the normalized signal was calibrated without considering the change of Brillouin line width under different temperatures of the water. In this work, the normalized signal of edge technique was re-calibrated basing on temperature dependence of the line width of Brillouin scattering in water. A more accurate relationship between Brillouin shift and the normalized signal was obtained. PACS 42.68.Wt; 42.79.Qx; 78.35.+c     

水中受激拉曼散射的能量增强及受激布里渊散射的光学抑制

为提高液体介质中受激拉曼散射的输出能量,提出了通过温度调控来抑制受激布里渊散射的方法,设计了532 nm多纵模宽带脉冲激光泵浦的受激拉曼散射发生系统,测量了不同温度下水中前向受激拉曼散射及后向受激布里渊散射的输出能量,分析了水温、泵浦激光线宽及热散焦效应对受激拉曼散射输出能量影响的物理机制.实验结果表明:通过降低水温可实现对受激布里渊散射过程的有效抑制,同时减小热散焦效应带来的光束畸变,从而有效提高受激拉曼散射的输出能量.研究结果对液体介质中的受激拉曼散射多波长转换具有重要意义.     

受激布里渊散射脉冲压缩技术研究进展

受激布里渊散射（SBS）作为三阶光学效应广泛应用于激光组束、分布式光纤传感、布里渊激光器等领域。近年来,SBS脉冲压缩亦得到特殊关注。基于布里渊放大过程中的能量转移特性,SBS脉冲压缩技术能够将ns量级脉冲压缩至亚ns量级,峰值功率可提升1～2个数量级。系统介绍了SBS脉冲压缩基本理论,综合论述了SBS压缩器结构、增益介质、泵浦脉冲等因素对脉冲压缩特性的影响,并对SBS脉冲压缩发展趋势进行了展望,为今后SBS特性的研究提供了有益参考,也为高重频、高能量激光的获取提供了可行方案。