苯的二级相干反斯托克斯喇曼散射(CARS)

设计了一套光路布置使用受激喇曼散射为相干光源,泵浦光子同受激光子之间混频,观测到苯的相干反斯托克斯喇曼散射共振现象,并获得很强的第二级相干反斯托克斯喇曼线.     

相干喇曼散射光谱技术

引言相干喇曼光谱学(相干反斯托克斯喇曼散射 CARS 和相干斯托克斯喇曼散射 CSRS,统称为相干喇曼散射 CRS)引起了人们极大的兴趣。尤其是相干反斯托克斯喇曼散射光谱技术,以其高效率、高灵敏度、高分辨率、抗荧光干扰性强、信息量大、应用范围广等著称。因此,成为分析、检测、研究分子结构及高阶光学声子激发态的有力工具。CRS光谱学的技术基础是相干激发和可调谐激光技术。CRS 现象的发生是基于介质的三阶     

相干反斯托克斯喇曼散射实验初步取得成果

相干反斯托克斯喇曼散射是一种比自发喇曼散射转换效率高得多的非线性过程。由于可调谐染料激光器日趋成熟及商品化,使相干反斯托克斯喇曼光谱(CARS)近几年来在国外得到颇为迅速的发展,成为一种具有高光谱分辨率和高空间分辨率的新颖光谱技术,引起人们广泛的兴趣。     

氢中后向一、二阶反斯托克斯受激喇曼散射

本文观察到氢的后向一、二阶反斯托克斯受激喇曼散射,分析了它们产生的机理,并比较了前向和后向受激喇曼散射的特性。     

相干反斯托克斯喇曼散射光谱方法的化学应用研究

本文介绍了采用宽带染料激光的相干反斯托克斯喇曼散射光谱技术。实验结果证明,利用这一技术可同时记录CARS和CSRS谱图,在吡啶的情况下,同时记录一条以上的喇曼谱线也是可能的。     

用光纤获得十级受激喇曼散射

本文报导了用多模光纤获得受激喇曼散射的实验研究。用480米长、多模、低损耗的梯度型石英光纤,用重复率为5次/秒和10次/秒、脉宽7毫微秒、功率0.7兆瓦的 YAG:Nd 倍频532毫微米的激光泵浦,获得了从546～702毫微米的十级斯托克斯受激散射。     

H_2中喇曼散射反斯托克斯锥角环状分布的观察

实验中用红宝石激光做泵浦,用高压H_2作为散射介质,注重观察一阶反斯托克斯散射光AS锥角环状分布及轴向分布的规律性。 喇曼散射中反一级斯托克斯光AS是由喇曼跃迁行为及四波混频作用这两种不同的形成     

缩略词选登(三)

ACF autocorrelation function 自相关函数ATC automatic thresholdlevel control 自动阀值电平控制BPSK binary phase-shiftkeyed 二进制移相键控的CARS coherent anti-Stokes Raman scattering 相干反斯托克斯喇曼散射CARS coherent anti-Stokes Raman spectroscopy 相干反斯托克斯喇曼光谱学     

液氮的受激喇曼散射研究

本文使用染料测Q红宝石激光激励液氮的受激喇曼散射，观察到一级斯托克斯、一级反斯托克斯和二级反斯托克斯线，测得散射光的喇曼频移、线宽、能量转换率和退偏振度等参数．并对所得结果进行了讨论。     

光纤传感技术用于铁轨温度监测的研究

对光纤喇曼散射技术用于铁轨温度监测的方法进行了理论和实验研究。采用大功率半导体脉冲激光器为泵浦光源和背向散射法对光纤中的背向喇曼散射（斯托克斯散射和反斯托克斯散射）进行测量。缠绕式光纤传感器模式中采用结果表明，该方法对采用传统方法难以实现的铁轨温度进行监测是可行的，且具有结构简单、成本低廉以及与结构兼容性好的优点。     

Laboratory study of polarized microwave scattering by surface wavesat grazing incidence: the influence of long waves

Laboratory measurements of microwave scattering at grazing incidence from superposed wind and weakly nonlinear (AK<0.024) regular long waves are presented. This study is an extension of previous measurements with wind waves only. A dual polarized (VV, HH) coherent pulsed Ku-band (14 GHz) scatterometer with temporal resolution of 3 ns was used to obtain Doppler spectra and the absolute cross section of scattered signals for grazing angles from 6° to 25° and winds in the range 2-12 m/s. A wire wave-gauge array was used to measure the wind-wave field. Measurements of the frequency and amplitude modulation of the scattered signal due to the long waves showed that the data separated into two groups. The first grouping corresponded to HH scattering in the upwind direction and was clearly associated with scattering from the dominant gravity wind-waves on the crests of the long waves. In this case, the wind speed clearly influences the frequency modulation due to long waves. The second grouping corresponded to scattering in the downwind direction and was consistent with Bragg scattering from higher frequency waves. In this case the frequency modulation due to orbital velocity of the long waves was found to be weakly dependent on wind speed over the range of parameters studied. This classification of the electromagnetic scattering was consistent with comparisons of direct and Doppler measurements of the kinematics of the surface wave field     

Radiophysical investigations of sea roughness (radiooceanography) at the Ukrainian Academy of Sciences

Experiments on the scattering of radio waves in the range 200 m to 3 cm from a rough sea surface are described. Amplitude, frequency, and space-time characteristics of scattered radio signals at different states of the sea surface are presented. It is shown that the problem of the short and medium wave scattering from the sea can be solved by the perturbance method. In this case the mechanism of scattering is of "resonant" character. The intensity of the backscatter signals is proportional to the density of the spatial spectrum on the half-length of the radio waves. The high frequency radio wave scattering is well described by a two-scale model of the scattering surface, "ripple on the large wave." The intensity of scattered radio signals is also proportional to the spectrum density of "ripples" whose length is approximately equal to half a radio wave. The effect of the large waves is to modulate the amplitude of a scattered radio signal and to broaden its frequency spectrum. Methods of solution of the reverse problem were considered. This allowed determination of parameters of sea roughness by characteristics of scattered radio signals. The principles of design of the corresponding equipment are described.     

Scattering from lossy dielectric objects buried beneath randomlyrough ground: validating the semi-analytic mode matching algorithm with2-D FDFD

A new semi-analytic mode matching (SAMM) algorithm is verified by two-dimensional (2-D) finite difference frequency domain (FDFD) simulations of scattering resulting from uniform plane waves incident on randomly rough dielectric half-spaces containing buried dielectric targets. The SAMM algorithm uses moderately low-order modal superpositions of cylindrical waves, each of which satisfies the 2-D-Helmholtz equation in its appropriate region (air, ground, or mine) and then matches all nonzero electric and magnetic field components at each interface by inverting a highly overconstrained dense linear matrix equation by singular value decomposition. That is, the set of cylindrical mode coefficients is found which best fits the boundary conditions in a least squares sense. For smooth ground, coordinate scattering centers (CSCs) are chosen at the mine center and at its image above the plane to model scattering. For randomly rough ground, additional CSCs are located within the rough boundary layer. Excellent agreement between 2-D-FDFD and the 2-D version of SAMM is observed, with 2-D-SAMM being at least an order of magnitude faster. 3-D-SAMM is estimated to be four orders of magnitude faster than 3-D-FDFD, with drastically reduced memory requirements     

掺铒石英光纤中的受激拉曼散射及受激四光子混频

报道了掺铒光纤受激拉曼散射（ＳＲＳ）和受激四光子混频（ＳＦＰＭ）的实验研究。所用光纤长为１０ｍ，泵浦源为ＮｄＹＡＰ倍频５３９．７ｎｍ脉冲激光，脉冲能量为０．１Ｊ，脉宽为５０ｎｓ，获得了从５５２．１～６２２．８ｎｍ的６级受激拉曼散射谱和受激四光子混频的Ｓｔｏｋｅｓ（５４２．９ｎｍ）及反Ｓｔｏｋｅｓ（５３７ｎｍ）谱线。     

Electromagnetic scattering from a spherical nonuniform medium-part II: The radar cross section of a flare

The radar cross section for scattering of electromagnetic waves by a plasma having an electron concentration proportional tor^{-2}is calculated. The exact solution is compared with the scalar approximation. It is found that the exact solution can be orders of magnitude smaller than any of the usual approximations.     

基于瑞利散射的单端BOTDA系统温度特性研究

提出一种不受电光调制器传输曲线温度漂移现象影响的基于瑞利散射的单端布里渊光时域分析系统,并对系统所需的合成信号及温度特性进行分析,通过搭建单端布里渊光时域分析温度传感系统测量系统的温度特性.结果表明:通过测量布里渊增益谱获得的布里渊频移与温度呈良好的线性关系;由单端布里渊光时域分析温度测量系统获得的布里渊频移的温度系数为1.109 MHz/℃,与传统双端布里渊光时域分析系统获得的1.20 MHz/℃具有良好的一致性,在1.77 km光纤上可实现9.5m空间分辨率的温度传感测量.     

Laboratory study of polarized scattering by surface waves atgrazing incidence. I. Wind waves

Laboratory measurements of Ku-band scattering at grazing incidence are presented. This study was motivated by the need to understand the processes which significantly contribute to scattering at grazing incidence. A dual polarized (VV, HH) coherent pulsed Ku-band scatterometer with good temporal resolution (3 ns) was used to obtain Doppler spectra and the absolute cross-section of scattered signals for grazing angles from 6-12°, and winds in the range 2-12 m/s. Wire wave gauges were used to measure the wind-wave field. Measurements of the first few moments of the Doppler spectra (cross-section, central frequency and bandwidth) showed that the data separated into two groups. The first grouping corresponded to HH scattering in the upwind look direction, and was clearly associated with scattering from the dominant gravity wind-waves. The second grouping corresponded to HH scattering in the downwind look direction, and all VV scattering, and was consistent with Bragg scattering from free higher frequency waves. This classification of the electromagnetic scattering was consistent with comparisons of direct and Doppler measurements of the kinematics of the surface wave field. The electromagnetic classification was also consistent with asymmetries in the wave field which increased with increasing wind speed     

Dipolar resonance in the plane-wave scattering by an axially magnetized ferrite cylinder

The scattering of E-polarized plane waves by an infinitely long axially magnetized ferrite cylinder is investigated for the case in which the radius of the cylinder is small in comparison with the wavelength of the incident wave. The scattering amplitude is found to have a maximum at a single resonant frequency whose approximate expression in terms of the physical parameters is deduced.     

Solution of the inverse electromagnetic scattering problem in the resonance case

In the scattering process of electromagnetic waves from dielectric or conducting targets, one often encounters resonances in frequency in the returned echo signals. In previous studies on the scattering of acoustic and elastic waves, analogous resonant echoes were shown to contain a wealth of information on the properties of the scattering target, permitting, in fact, the complete solution of the corresponding inverse problem. The same is recognized to be the case for the electromagnetic scattering problem considered here. For the case of dielectric or coated conducting spherical targets, the spacing and the widths of the resonances are shown to determine the dielectric constant and the coating thickness of the target in a direct fashion.