利用斯托克斯参量验证偏振光

利用斯托克斯参量表示入射光的偏振特性,给出了斯托克斯各参量测量方法与计算原理,通过实验和关系转换,进而可更直观地判断光的偏振态.     

双折射光纤受激拉曼散射偏光特性的实验研究

对椭圆芯光纤受激拉曼散射偏光特性进行了系统的实验研究。实验巾观察到8级斯托克斯线和2级反斯托克斯线,对不同偏振态的抽运光激励下各级斯托克斯线的偏振特性、拉曼频移等参量进行了分析,并给出了经验公式。其结果与实验数据符合良好。实验表明,双折射光纤受激拉曼谱的各级斯托克斯线的偏振状态不但与拉曼介质有关还与抽运光的偏振态有关,入射抽运光偏振态对低阶次的斯托克斯线拉曼频移的影响较小,而对高级斯托克斯线拉曼频移影响较大。     

在与原子相互作用中光偏振态的量子描述及其演化

应用偏振光的量子理论和斯托克斯算符研究了无克尔媒质和存在克尔媒质情况下，光在与原子相互作用过程中偏振态的演化.研究了偏振光中斯托克斯参量的涨落及其压缩的非经典行为.偏振椭圆、量子光学中的偏振度和斯托克斯参量的信噪比也得到了讨论.结果表明斯托克斯参量及其涨落在时间演化中呈现出被调制的振荡，这些振荡表现出间歇地崩塌和恢复.在与原子的相互作用过程中，光的偏振椭圆不随时间变化，但偏振度却随时间出现振荡.克尔媒质对这些振荡演化有很大影响. 关键词： 斯托克斯算符 斯托克斯参量 量子偏振态 量子涨落     

拉曼效应对低双折射光纤偏振特性的影响

在低双折射光纤中,利用线偏振光满足的包含拉曼效应的非线性耦合模传输方程,通过引入斯托克斯参量,导出了斯托克斯参量所满足的耦合模传输方程.利用庞加莱球图示法,描述了拉曼增益效应作用下光波偏振态的演化,研究分析了拉曼效应对低双折射光纤中光波偏振态演化规律的影响.结果表明,当输入功率与运动常量满足一定关系时,拉曼增益效应改变了光波传输时其偏振态演化周期和偏振态的椭圆率.     

一种反射式扭曲向列型液晶显示优化设计的新方法

基于扭曲向列型液晶的显示器件通过调制光波的偏振态实现显示的目的,因此光波的偏振状态在其中起了极为关键的作用.本文结合琼斯矩阵和表示光波偏振态的斯托克斯参量j-circle方法,提出了一种优化反射式扭曲向列型液晶显示器件的新方法.该方法与原有的空间参量方法不同的是采用了追踪光波在传播过程中偏振态变化的办法得到反射式液晶显示器件中各光学元件的参数.该方法简单直观并且可以对多个参数同时进行优化,实现了显示性能的最优化设计并得到了新的显示模式.     

基于斯托克斯参量测量的偏振共焦显微成像技术的研究

提出了一种基于斯托克斯(Stokes)参量测量的偏振共焦显微成像新方法。以斯托克斯参量、偏振度、相位差、方位角和椭率角等偏振参量作为成像物理量,通过系统集成方法将斯托克斯参量测量系统整合到共焦显微成像系统,通过共焦显微成像系统的显微物镜将激光聚焦到样品表面,而带有样品偏振信息的反射光进入斯托克斯参量测量系统进行偏振测量,把从斯托克斯参量测量系统中出射的4个斯托克斯光分别聚焦到4个点探测器进行光电探测,实现斯托克斯参量的共焦探测,同时获得同一物点的4个斯托克斯参量以及偏振度、相位差、方位角和椭率角等偏振参量。对样品进行二维扫描,获得不同物点的4个斯托克斯参量及其相关的偏振参量,利用计算机软件进行图像重建,从而获得样品的斯托克斯参量及其相关偏振参量的共焦显微图像。     

基于数字全息及复用技术的全场偏振态测试方法

提出了一种在数字全息记录系统中利用偏振和角分复用技术对光场进行偏振态检测的方法. 将全息系统中的一束参考光分为偏振方向相互正交、初相位相同的两束光, 并分别与物光相同偏振方向的两个分量干涉, 形成两幅子全息图, 同时记录在一帧画面中. 为了分开记录到的物光两个分量, 系统中利用了角分复用技术, 即在两束参考光中引入不同载频, 使物光两分量的频谱位于全息图频谱面的不同区域. 通过滤波、逆傅里叶变换和衍射计算, 获取距离全息图不同位置处物光两正交分量复振幅信息. 利用复振幅信息, 可以构建被测物光的斯托克斯参量和琼斯矢量, 从而表征物光的偏振态. 实验中, 通过对一束椭圆偏振光进行偏振态测量以及对该光束在不同空间位置处的偏振态进行表征, 表明该方法可以实现光束偏振态全场测试, 并且具有较高的可靠性. 关键词： 数字全息 偏振态 琼斯矢量 斯托克斯参量     

光的偏振与色散

讨论了光纤线路中两偏振主态与补偿器中偏振分束器主轴的对准问题,给出了偏振分束器任何一个主轴上光强的表示并推导出相应的电功率信号表示式,建立了电功率与光信号两个模式之间的延迟时间以及偏振主态与分束器主轴相对角度的变化关系。初步实验表明.可以通过偏振控制器或可转动的光纤连接器实现偏振主态与偏振分束器的对     

低双折射光纤中拉曼增益对光偏振态的影响

利用包含拉曼增益的耦合非线性薛定谔方程, 导出了斯托克斯参量表示的含拉曼增益的杜芬方程, 通过椭圆积分求出了杜芬方程的解析解, 重点分析了光波在低双折射光纤中传播时, 拉曼增益对其偏振态演化的影响结果表明当输入功率与运动常量满足一定关系时, 拉曼增益改变了光波传输时其偏振态演化周期.     

高双折射光纤中非线性耦合模偏振态稳定性分析

通过高双折射光纤中非线性耦合模传输方程,首先,利用斯托克斯参量,用庞加莱球研究分析了耦合模传输的稳定性及偏振态的演变,结果表明高双折射光纤中耦合模的传输不产生分歧现象,传输具有稳定性;其次,描述了拉曼效应对各种状态下偏振态演变规律的影响,给出了斯托克斯参量S₁,S₂与S₃的解析解及拉曼效应对偏振态的演变周期的影响.     

Polarization analyzers operating in a wide spectral range

Different versions of practical realization of customary optical systems for full measurement of the polarization state of quasi-monochromatic partially polarized light are considered. They can be used to overcome measurement difficulties associated with the finite width of the spectral range being studied. The effect of changes in characteristics of optical and polarization elements over a spectral range on the character of polarization measurements is analyzed. Methods for elimination of chromatism or taking into account its effect on measurements are suggested. Relations for taking into account the effect of chromatism of a phase plate with constant thickness on measurement results are given. Operation of a classical four-channel scheme for studing quasi-monochromatic partially polarized light in the visible and near-IR regions is considered. For this system, expressions are derived which make possible determination of Stokes parameters taking into account the effect of a finite spectral range. A system using phase modulation of radiation by an electrooptical cell and measurement of the maximum and minimum intensities of the modulated signal is considered. Measurements are carried out by using a two-channel system. Expressions are derived which make possible determination of Stokes parameters for the system under consideration in the visible and near-IR spectral regions. A system for measuring the polarization state of radiation in the visible and near-IR regions and based on modulation of radiation by an electrooptical phase cell is described. Measurements are carried out for the fundamental modulation frequency and its harmonics using a two-channel scheme. Relations for determining Stokes parameters of the system are presented.     

高光谱偏振成像全Stokes参量获取新方法

考虑到现有Stokes参量获取方法测量速度慢、测量精度低、系统结构复杂等特点,提出了一种基于双液晶可调相位延迟器(liquid crystal variable retarder,LCVR)和声光可调滤波器(acousto-optic tunable filter,AOTF)的光谱偏振成像系统中全Stokes参量的新获取方法。从AOTF和LCVR的工作原理出发,介绍了系统的基本探测原理;根据偏振分析提出了快速获取全Stokes参量的新方法--该方法选取四个固定的LCVR控制电压,同时控制两个相同的LCVR对光波进行相位调制,得到四组(八个)两两相同的相位延迟量即可求得Stokes参量。此外,设计了能够稳定输出均方根为0~+8.72 V连续可调方波的LCVR控制器,并对其进行定标,实现了不同波长下光波的精确调制。搭建实验样机,以偏振方向分别为0°,90°和45°的三个偏振片P₁,P₂,P₃作为偏振测量目标,测得了波长为632 nm时的全Stokes参量图;以画有夹角为30°的红色、绿色、蓝色三色线条的实验板作为光谱测量目标,对400～750 nm光谱范围的71个通道(光谱带宽为5 nm)进行光谱成像,得到了与红色、绿色和蓝色的分析谱段范围相一致的光谱曲线。结果表明,该系统不仅可以快速准确地获取全部Stokes参量,而且系统结构简单、成像质量良好。     

On vector radiative transfer equation in curvilinear coordinate systems

The differential operator of polarized radiative transfer equation is examined in case of homogeneous medium in Euclidean three-dimensional space with arbitrary curvilinear coordinate system defined in it. This study shows that an apparent rotation of polarization plane along the light ray with respect to the chosen reference plane for Stokes parameters generally takes place, due to purely geometric reasons. Analytic expressions for the differential operator of transfer equation dependent on the components of metric tensor and their derivatives are found, and the derivation of differential operator of polarized radiative transfer equation has been made a standard procedure. Considerable simplifications take place if the coordinate system is orthogonal.     

通道调制型偏振成像系统的偏振参量重建

通道调制型偏振成像系统中,焦平面上获取的信息需要通过目标偏振参量的重建才能有效提取,因而重建是目标识别、材料分析、生物医疗等技术进一步应用的前提.为了实现在非理想情况下通道调制型偏振成像系统的偏振参量精确重建,需要解决成像系统中电荷耦合器件(CCD)采样频率与频谱位置偏移对重建的影响.本文首先详细分析了频谱不发生混叠的条件:CCD采样频率应至少为4倍基频;在偏振干涉频谱位置偏移时,使用最大频谱法确定各个偏振态的载波频率,通过频移、滤波和傅里叶变换获得目标的偏振重建二维图像;最后通过计算机模拟仿真与实验分析结合的方法验证该重建方案的可行性与有效性.模拟与实验结果表明:改进后的偏振重建法得到的偏振图像与原始输入图像的均方差在0.001以下,峰值信噪比有明显的提高,且结构相似度可达到0.9以上,表明该方法获得的二维偏振态重建图像精度高,与理论偏振解调法相比具有很大的优越性.该工作希望为后续偏振探测与分析进一步的研究提供参考.     

Experimental study on the Stokes effect in disordered birefringent microstructure fibers

In this paper, a 120-fs pulse transmission experiment is carried out using disordered birefringent microstructure fibers with cladding ventages. Through this experiment, it is found for the first time that remarkable Stokes and anti-Stokes waves can also be produced when the central wavelength of the incident pulse is in the normal dispersion regime of the microstructure fiber. The generation of the two waves can be explained by the four-wave mixing phase matching theory. Properties of the two waves under the action of femtosecond laser pulses with different parameters are studied. The results show that the central wavelength of anti-Stokes waves and Stokes waves produced under the two orthogonal polarization states shift by 63 nm and 160 nm, respectively. The strengths and central positions of the two waves in birefringent fibers can be controlled by adjusting the phase match condition and the polarization directions of incident pulses.     

分振幅型全Stokes同时偏振成像系统波片相位延迟误差分析

分振幅型全Stokes同时偏振成像仪具有实时性好、空间分辨率高、精度高等优点,有很高的应用价值.分振幅型全Stokes同时偏振成像系统利用偏振分束器、1/2波片和1/4波片将入射光Stokes矢量调制在4幅图像中,可解析入射光Stokes矢量. 1/2波片和1/4波片的相位延迟误差对Stokes矢量测量精度有着不可忽略的影响.建立了包含上述两种误差的Stokes矢量测量误差方程,分析了1/2波片和1/4波片相位延迟耦合误差对自然光、0°/45°线偏光、左旋圆偏光等典型基态入射光的Stokes矢量测量误差的影响,推导了任意偏振态的Stokes矢量测量误差的表征方法.在邦加球球面和球内选取不同偏振度的Stokes矢量作为入射光进行仿真.结果表明, Stokes矢量测量误差和偏振度测量误差均随着入射光偏振度的增大而增大.选取入射光偏振度为1时的偏振测量精度评估系统.为满足2%的偏振测量精度, 1/2波片相位延迟误差应在±1.6°内, 1/4波片相位延迟误差应在±0.5°内.这对提高系统的偏振测量精度具有重要意义,为系统设计和研制提供了重要的理论指导.     

On the derivation of vector radiative transfer equation for polarized radiative transport in graded index media

Light transport in graded index media follows a curved trajectory determined by Fermat's principle. Besides the effect of variation of the refractive index on the transport of radiative intensity, the curved ray trajectory will induce geometrical effects on the transport of polarization ellipse. This paper presents a complete derivation of vector radiative transfer equation for polarized radiation transport in absorption, emission and scattering graded index media. The derivation is based on the analysis of the conserved quantities for polarized light transport along curved trajectory and a novel approach. The obtained transfer equation can be considered as a generalization of the classic vector radiative transfer equation that is only valid for uniform refractive index media. Several variant forms of the transport equation are also presented, which include the form for Stokes parameters defined with a fixed reference and the Eulerian forms in the ray coordinate and in several common orthogonal coordinate systems.