偏振度作为反馈信号进行偏振模色散补偿的研究

对40Gb／s光纤通信中归零码和非归零码光脉冲的偏振度随二阶偏振模色散的变化规律进行了数值模拟,结果表明由于二阶偏振模色散的影响,偏振度的变化趋势呈现出震荡性,二阶偏振模色散对归零码的偏振度要比非归零码的偏振度影响明显;同时搭建了偏振模色散补偿系统,对系统进行数值模拟和实验所得到的结果都表明,以偏振度作为反馈信号,采用粒子群优化算法作搜索算法能够有效地对归零码和非归零码系统的一阶及高阶偏振模色散进行自适应补偿。     

Active polarization imaging system to discriminate adaptively with diagonal Mueller matrix

A promising method to optimize the polarization state of two-channel active polarization imaging system is presented. In this method, it is seminal that the detecting function of the imaging system is regarded as a discriminant projection of the observed objects’ polarization features (elements of the Mueller matrix). The polarization state can be seen as a physical classifier which can be obtained by training samples. The image acquired with the system that has the designed optimal polarization state become discriminative results directly. The effectiveness of the proposed method and the discriminative ability of the optimal polarization state are demonstrated by the experimental results.     

基于偏振激光辅助照明的ICCD探测技术研究

为了验证偏振激光辅助照明ICCD探测目标的可行性,I以偏振成像探测原理为基础,提出一套基于偏振激光辅助照明的ICCD探测系统。该系统采用808 nm人眼不可见偏振激光辅助照明,ICCD对后向散射激光进行检偏和光电信息转换,实现背景中目标的偏振成像探测。通过在野外环境中对该系统的探测能力进行实验测试,结果表明,在0、45和90检偏角下,人造金属涂漆目标对照射偏振激光退偏小于10%;绿色背景对照射偏振激光退偏度约50%;沙土地面退偏度约30%,人造金属涂漆目标相对于自然背景随检偏角增大图像对比度也越大。     

水下物体激光圆偏振成象实验及与线偏振成象的比较

采用波长532nm激光作光源,面阵CCD作探测器,利用圆偏振技术进行水下物体成象实验研究,对实验结果进行了分析并与线偏振成象技术进行了比较。结果表明无论是采用圆偏振技术还是线偏振技术都可提高水下物体成象的衬比（度）和成象距离;水体较清时圆偏振成象清晰度远远大于线偏振成象清晰度;当水体较混时,圆偏振成象清晰度大大下降和线偏振成象效果相接近。     

基于Stokes矢量的实时偏振差分水下成像研究

偏振差分水下成像能够有效地克服光散射效应造成的图像退化问题, 在水下物体探测与识别领域具有重要应用价值. 传统的偏振差分方法靠光学检偏器的无规则机械转动来实现对散射背景的共模抑制, 限制了其在水下成像过程中的实时探测性能. 本文通过分析偏振差分探测原理来建立偏振差分成像模型, 从理论上提出了基于Stokes矢量的计算偏振差分水下实时成像系统, 并进行了实验验证. 研究结果表明, 基于Stokes矢量的计算偏振差分成像不仅与传统的偏振差分方法具有相同的水下探测效果, 更重要的是可以实现快速成像过程. 该方法可以应用到目前的偏振成像仪器系统, 实现无需人-机互动的自动化实时偏振差分水下成像, 进一步提高水下物体探测与识别的效率.     

基于可调偏振度源的PSIM偏振光谱仪线偏振度测量结果定标校正

提出了一种基于可调偏振度源的偏振定标方法,利用方法完成了基于偏振光谱强度调制(PSIM)技术偏振光谱仪的线偏振光偏振度测量结果定标校正。以可调偏振度源输出的不同偏振度的线偏振光作为待测光源,用PSIM偏振光谱仪测量待测光源输出得到原始数据。将原始数据解析处理得到的偏振度谱与待测光源输出的理论偏振度谱进行线性拟合,得到校正系数。利用该校正系数对PSIM偏振光谱仪的测量处理结果进行定标校正。结果表明:在有效测量波段内(500~650nm),定标校正后PSIM偏振光谱仪的线偏振度测量解析精度明显提高,与待测光源输出的标准偏振度值间的最大误差由0.017减小到约为0.003,基于可调偏振度源的偏振定标校正方法具有可行性。     

SU(2)非自治系统中的互补混沌——加速器中离子极化的稳定性

利用SU(2)代数动力学方程研究了加速器中带自旋离子的极化对磁场的含时无规扰动的稳定性问题,发现低度极化的系统对磁场无规扰动十分敏感,而高度极化的系统对磁场无规扰动比较稳定;自旋守恒导致自旋纵向分量的无规涨落和横向分量的无规涨落存在着互补性.这一结果表明,在产生离子束极化的实验中,在离子束低度极化的前期阶段,磁场应具有较高的稳定性,而在离子束极化度较高的后期阶段,磁场的稳定性要求可以放松;自旋纵向分量的无规涨落和横向分量的无规涨落的互补性有可能用来做成稳定离子极化的负反馈.     

径向偏振调制对聚焦光斑匀滑及偏振特性的影响

基于标量衍射理论建立了光谱色散平滑(SSD)、随机相位板(RPP)和偏振匀滑(PS)联用的光束匀滑方案数值仿真模型。以斑纹对比度和偏振度为主要评价参量,利用该模型研究了径向偏振调制的匀滑及消偏振特性。研究表明,径向偏振调制可以有效降低聚焦光斑斑纹对比度和偏振度。使用半波片拼接方式产生近似径向偏振光时,拼接单元数对匀滑及偏振特性影响较小,8片拼接的匀滑效果已与理想径向偏振光几乎一致。对比分析了径向偏振调制、正交偏振调制和双折射楔三种PS方式,结果表明,由于三种PS方式本质上的一致性,光束的匀滑及偏振特性差别较小。     

低轨空间目标地基偏振成像系统偏振定标方法

针对地基大口径望远镜的机上自适应光学系统构建的低轨空间目标偏振成像系统,提出一种基于非偏振标准星和机上起偏装置的宽带偏振定标方法。该方法以非偏振标准星作为光源,并在望远镜系统的一次像面处加入起偏装置对入射光的偏振态进行调制,再结合基于非线性最小二乘拟合的偏振定标方法分两步对整个偏振成像系统进行宽带偏振定标。为验证该偏振定标方法的效果,利用Matlab软件基于相干矩阵和偏振追迹构建了相应的模型进行仿真分析,仿真结果表明该偏振定标方法可以有效减小望远镜系统偏振效应对偏振探测准确性的影响,并且偏振定标元件的初始角度误差在±5°范围内时对偏振定标准确性的影响极小。     

Spatial polarization sensitivity of single Au bowtie nanostructures

Metallic bowtie nanostructures as plasmonic nanoantennas can create highly enhanced local fields when resonating with the incident light. With Au bowtie nanostructures fabricated by lithography method, we experimentally observed that the photoluminescence (PL) spatial profile from a single Au bowtie nanoantenna was strongly dependent on the excitation light polarization. While varying the incident light polarization, the spatial distribution of the PL intensity in the nanogap of an Au bowtie changed as predicted by the simulation results on the electromagnetic field enhancement distribution. The polarization feature of the PL intensity relative to the polarization direction of incident excitation light was also discussed. The study may find application in the design of polarization sensitive plasmonic sensors.     

Analytical approach to the impact of polarization aberration on lithographic imaging

An analytical approach to the impact of polarization aberration on lithographic imaging is proposed. The linear relationship between image placement error (IPE) of alternating phase-shifting mask (Alt-PSM) and odd aberration items of polarization aberrations, as well as that between best focus shift (BFS) of Alt-PSM and even aberration items of polarization aberrations are established by analytical equations, respectively. The validity of the linear relationships is demonstrated by numerical results. The differences and connections between scalar aberration and polarization aberration are briefly discussed based on these linear relationships.     

偏振遥感在伪装目标识别上的应用及对抗措施

 为了研究偏振遥感对伪装目标的识别特点,分别对不同颜色的伪装网进行了偏振参数测量和成像实验。通过数据分析发现,伪装网的散射偏振度受观测条件和材料自身特性（如反射率、折射率和表面粗糙度）影响很大;伪装涂层对入射光的散射作用可以分为面散射和体散射,其中面散射具有起偏振作用而体散射具有消偏振作用;与自然背景相比,伪装目标的偏振特征非常显著,利用偏振遥感可以有效地识别出常规侦察手段所不能发现的伪装目标。通过偏振遥感的侦察原理和特点分析,提出了可以利用表面结构设计和烟雾等方法对抗偏振遥感的侦察。     

High proton polarization by microwave-induced optical nuclear polarization at 77 K

Protons in naphthalene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively, at liquid nitrogen temperature in a magnetic field of 0.3 T by means of microwave-induced optical nuclear polarization. The polarization was measured by nuclear magnetic resonance as well as by the neutron transmission method. The relaxation time of the proton polarization at 0.0007 T and 77 K was found to be almost 3 h and the polarization enhancement reached a record value of 8x10(4). The usefulness of the method in many areas of physics and chemistry is discussed.     

General demonstration of principal states of polarization and real-time monitoring of polarization mode dispersion in optical fibres

We investigated the general properties of polarization effects in optical fibres and demonstrated the existence of socalled principal states of polarization (PSP), which mean the fixed points in mathematics, in different polarization effects,such as birefringence and polarization mode dispersion, by using fixed point theory. Furthermore, a time evolution vector is defined to describe the time evolution of polarization state in optical fibres, which is used to investigate the time evolution of polarization mode dispersion vector (PDV), including differential group delay and PSP. The experimental results of real-time monitoring of PDV by using this method are reported. To our knowledge, this is the first report on monitoring PSP evolution in optical fibres.     

Analysis of the Polarization Influence on the Erbium-Doped Fiber Laser Transient Behavior

Abstract

We studied the erbium-doped fiber laser transient behavior dependence on the pump polarization state or on the cavity polarization eigenvalues. Several series of measurements are shown in which the changes in the transient laser response can be appreciated as the pump polarization state, or the cavity polarization eigenvalues are modified by means of polarization controllers. Results are fitted to a model considering polarization hole burning. It is shown that including this effect is fundamental for a correct erbium-doped fiber laser transient model. On the other hand, the validity of the model's fitting parameters under pump or cavity polarization changes is analyzed.     

Photon energy dependence of the spin polarization

Spin polarization in semiconductors was investigated by pump-probe measurements, where the transmissions of the samples were monitored with probe pulses with same and opposite circular polarizations. The spin polarization as a function of the pump-probe delay was estimated, and the polarization was found to decay in a sub-ns timescale. It was also found that the polarization depends strongly on photon energy of the pump beam. The pumping energy dependence of the spin polarization was discussed based on the inter-band transition probabilities.     

高消光比多偏振态光源系统设计

在现代工程测量中,由于工程的各项技术指标要求越来越高,相应地对光源也提出了更高的要求。依据晶体双折射和晶体相位延迟对光偏振态的影响以及光的折射角与光振动方向有关的原理,设计了高消光比多偏振态光源系统,并设计测试方案对该系统实现的偏振态和消光比进行了验证。该光源系统通过计算机精密控制电机旋转设计的转盘结构很方便快捷地实现了S偏振态、P偏振态和圆偏振光的输出,并且系统中设计了平移和旋转装置自动控制偏振棱镜,获得了高消光比的偏振光,出射光消光比小于等于510-6。     

亚波长光栅的偏振闪耀特性

 使用琼斯矩阵的方法推导了连续结构亚波长光栅的衍射方程,给出了光栅衍射效率表达式,对偏振特性与衍射特性进行了研究。发现连续结构亚波长光栅仅存在３个衍射级,总衍射效率为100%,且衍射效率可在衍射级间任意分配,0级的偏振态与入射光的偏振态相同,±1级衍射光偏振态与入射光无关,－1级为左旋圆偏振光,＋1级为右旋圆偏振光。通过设置入射光偏振态与光栅相位延迟等参数,可使光栅具有闪耀特性,据此可用于设计高效偏振光分束器和偏振光开关。     

Passive component based multifunctional Jones matrix swept source optical coherence tomography for Doppler and polarization imaging

We present a fiber based multifunctional Jones matrix swept source optical coherence tomography (SS-OCT) system for Doppler and polarization imaging. Jones matrix measurement without using active components such as electro-optic modulators is realized by incident polarization multiplexing based on independent delay of two orthogonal polarization states and polarization diversity detection. In addition to polarization sensitivity, this system measures Doppler flow without extra hardware for phase stabilized SS-OCT detection. An eighth-wave plate was measured to demonstrate the polarization detection accuracy. The optic nerve head of a retina was measured in vivo. Detailed vasculature and birefringent structures were investigated simultaneously.