Mathematical principle and characteristics of polarization transform

The precise definition of polarization transform is proposed from the viewpoint of polarization domain transform for the first time. The mathematical principle, characteristics and physical meanings of polarization transform are analyzed. Two typical kinds of polarization transforms which are called unitary matrix polarization transform (UMPT) and diagonal matrix polarization transform (DMPT) are put forward. The gain property and the change property of polarization state distance are presented in detail. Thereby, the concept of serial polarization transform is proposed. A general polarization transform can be realized by two steps: changing the location of polarization states in polarization domain by UMPT; and expanding or compressing the density of polarization states by DMPT. The result is meaningful to many applications including polarization filtering, detection, enhancement, anti-jamming, discrimination and so on. Supported in part by the National Excellent PhD Dissertations Fund of China (Grant No. 08100101), the New Century Excellent Talents Fund of China (Grant No. NCET-04-0997), the National Natural Science Foundation of China (Grant No. 60672033) and the Excellent PhD Fund of National University of Defense Technology (Grant No. B070401)     

Transformation of the polarization structure of laser radiation in optical systems

A range of questions regarding the calculation of the spatial polarization structure of laser radiation in optical systems is considered. It is shown that polarization aberrations in such systems lead to a distortion of the initial polarization structure. Requirements for an optical system intended for the transmission of the polarization structure of laser radiation and methods for the compensation of polarization aberrations are discussed.     

Manifestation of anisotropic collisional generation of higher polarization moments in polarization of quadrupole emission

Direct observability of polarization moments of a higher order—octupole orientation of atomic angular momenta (κ=3) and their hexadecapole alignment (κ=4)—from polarization of quadrupole radiation is discussed. The case when atoms are excited through dipole absorption of light producing orientation or alignment of angular momenta with κ=1 or 2 and higher polarization moments are induced by collisions with a beam of particles is considered. It is shown that differences in the laws of transformation of polarization moments of various ranks κ in rotations of coordinate axes allow us to select the pure contribution of the higher polarization moment under study from the signal of polarization of quadrupole emission by excluding the contribution of orientation or alignment with κ=1 or 2. Optimum systems of coordinate axes for the observation of octupole orientation from circular polarization of light and for the observation of hexadecapole alignment from linear polarization of light, in which the pure contribution of the higher polarization moment under study to polarization of quadrupole emission reaches its maximum, are calculated.     

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。     

光源偏振度对光纤陀螺零漂影响的研究

以Y波导集成光学调制器保偏型干涉式光纤陀螺作为研究对象,根据各光学元器件的参数建立了各器件的琼斯矩阵以及光路传输模型,在此基础上进行了光路偏振误差的理论分析。通过推导,得到了保偏型干涉式光纤陀螺的偏振误差表达式,并首次分析了光源偏振度对光纤陀螺零漂的影响。借助光源尾纤输出的光谱,对由0%~3%之间呈线性变化的偏振度以及对经实验测试的光源偏振度的实际值引起的偏振模式耦合误差的零漂值进行了仿真计算。结果表明,当光路中其它参数不变时,由光源偏振度变化引起的零漂值为0.001°/h,满足了高精度光纤陀螺的精度要求。     

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。     

The method of polarization tomography of radiation in quantum optics

The essence and basic structural elements of the method of polarization tomography of quantum radiation (the reconstruction of the polarization states of a field solely from polarization measurements) are described. The essential features of the method are discussed in comparison with usual field and spin tomographies. A general scheme for experimentally implementing this method is suggested and its use in polarization tomography of biphotonic radiation with hidden polarization is briefly analyzed.     

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。     

Application of radiative electron capture for the diagnostics of spin-polarized ion beams at storage rings

It is proposed to apply the radiative electron capture into high-Z projectiles as a probe process for measuring the spin polarization of the hydrogenlike ions at storage rings. We argue that such polarization measurements are possible since the linear polarization of emitted x-ray photons is greatly sensitive to the spin states of incoming ions with nuclear spin I > 1/2. In particular, for K-shell electron capture into the hydrogenlike ions, the linear polarization of light as measured out of the reaction plane is found to be proportional to the degree of ion polarization. Detailed computations for the dependence of the photon polarization on the ion spin states and projectile energies are carried out for the electron recombination into hydrogenlike Bi 82+ ions.     

海面太阳耀光背景下的偏振探测技术

为了实时抑制太阳耀光对海面目标探测的影响,基于偏振光学理论,设计并构建了一套偏振自适应滤波探测系统。本文介绍了偏振探测系统的功能和组成、偏振探测及背景抑制原理,并给出了该系统的光学设计结果;利用自适应偏振滤波探测系统,通过搭载望远镜跟踪试验平台,针对海上典型目标,开展了相关的偏振验证实验。实验结果表明:海面太阳耀光存在比较明显的偏振特性,采用常规探测手段,探测器极易出现饱和,而利用偏振探测技术则能够有效抑制太阳耀光的影响,进而实现目标的有效探测。     

血液静态荧光偏振光谱研究

报道了用408 nm的LED偏振光诱导浓度为0.3%的人全血溶液在350800 nm波段的静态荧光偏振光谱,讨论了其光谱的结构特征和红移现象并给出了机理解释;检测了不同浓度全血溶液荧光偏振光谱中在490nm和610 nm附近处两个各主要荧光区的偏振度,实验结果表明,当血液浓度为1.0%时,在两个主要荧光区的偏振度分别为0.4796和0.4344,当浓度增加到8.0%时,相应的偏拓坟墓分别为0.2064和0.0538。研究了偏振度随浓度的变化规律,用能量转移理论分析了在不同荧光区、不同浓度下,血液中各荧光团之间的不同能量转换机理及偏振度的变化现象。研究结果对光诱导生物组织自体荧光诊断技术有一定的参考价值。     

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.     

1550nm-VCSELs在偏振保持光反馈和正交光注入下的偏振转换特性

基于自旋反转模型,研究了1550 nm垂直腔面发射激光器(1550 nm-VCSELs)在偏振保持光反馈和正交光注入下的偏振转换特性.结果表明:正交光注入下的从激光器会随着注入强度的增加产生偏振转换.在归一化注入电流较小时,改变反馈强度,会使从激光器发生偏振转换的注入强度出现规律不同的变化;改变频率失谐,会使从激光器发生偏振转换的注入强度出现规律相同的变化.     

Generation of radially polarized light beams of high quality using a step-index optical fiber

We present an experimental setup to generate radially polarized beams without using high-cost optical elements. In the setup a four-segment polarization converter is used in front of the fiber to produce a pseudo radially polarized beam. A traditional step-index fiber which supports only LP₀₁ and LP₁₁ modes is then used as a mode-cleaning device. A commercial mechanical fiber-squeezer polarization controller is applied to produce adequate pressure and twist onto the fiber. The four-segment polarization converter and the fiber squeezer polarization controller are adjusted by turns for improving the beam quality in intensity and polarization. Additionally, several methods of characterizing the polarization properties of radially polarized beams are reviewed. One of the latest methods is applied for characterizing the polarization properties of the radially polarized beams produced by using our technique. The results show the highquality of the obtained beams.     

偏振对飞秒激光辐照LiF晶体的影响

飞秒激光聚焦到LiF晶体内部, 晶体的加工形貌随偏振改变. 实验表明, 偏振方向平行于<110> 晶向时, 加工起点到表面的距离是<100>偏振下的1.08 倍; 而<110>偏振下加工终点到表面的距离是<100> 偏振下的1.01 倍. 为了解释加工形貌的偏振依赖, 建立了逆韧致辐射、雪崩电离和无辐射跃迁的模型, 首先, 价带电子通过强场电离和雪崩电离, 从激光中吸收能量跃迁到导带, 该过程用电子密度演化方程和傍轴非线性薛定谔方程描述, 求解方程得到导带电子密度; 其次, 导带电子通过无辐射跃迁过程释放能量给晶格, 由能量守恒计算出晶格温度沿激光传播方向的分布; 最后, 晶格温度超过熔点以上的区域被加工. 模拟结果显示, <110>偏振下加工起点到表面的距离是<100> 偏振下的1.03倍, 而<110>偏振下加工终点到表面的距离是<100>偏振下的0.981 倍, 与实验结果基本一致. 虽然Z扫描技术测量的非线性折射率随偏振方向变化, 但是非线性折射率的变化趋势与实验结果相反. 模拟和实验证明逆韧致辐射导致加工形貌随偏振变化.     

Degree of polarization for single-photon beam in a turbulent atmosphere

The polarization fluctuations of single-photon beam propagation through the slant path turbulent atmosphere are studied. The Stokes operators and the degree of polarization of single-photon beam in a turbulent atmosphere are obtained. It is shown by analytical calculations, that the quantum degree of polarization of linearly polarization light is a decrease function of the atmospheric turbulence strength and the propagation distance for lower detection photon number.     

Reflectometric measurements of polarization properties in optical-fiber links

Polarization sensitive reflectometric techniques can be effectively used to perform spatially resolved measurements of polarization properties of fiber optic link — such as birefringence, polarization mode dispersion and polarization dependent loss. In particular, this contribution is focused on polarization sensitive OTDR and provides a survey of its theory and main applications. Special emphasis is given to the characterization of fiber birefringence, that allows to inspect the fiber while cabled and, consequently, to test and improve the cabling process. In addition, the analysis of the birefringence also allows to define reliable mathematical models, which are essential for the design of low polarization mode dispersion fibers. Reflectometric measurements of polarization mode dispersion and polarization dependent loss are also discussed.     

一种高功率折线栅极化转换天线罩的设计

设计了一种用于高功率径向线螺旋阵列天线的极化转换天线罩。利用三层介质层包夹双层金属折线,形成密封的埋入式折线栅结构。在实现圆极化与线极化相互转换的同时,又避免金属与空气接触,可以提高功率容量。分析了埋入式折线栅单元各参数的影响,并优化单元参数,以此构建埋入式折线栅极化转换天线罩并加载至X波段高功率径向线螺旋阵列天线,分析了天线的基本性能以及功率容量。仿真结果显示:天线匹配良好,增益和波束宽度变化很小,中心频率轴比由1.16 dB变为40 dB,圆极化波转换为线极化波效果良好;经初步分析,极化转换天线罩的功率容量为121 MW,实现了极化转换天线罩的高功率应用。     

Polarization ellipse and Stokes parameters of a stochastic electromagnetic Gaussian Schell-model beam propagating through a polarization grating

An analytical propagation formula for the cross-spectral density matrix of a stochastic electromagnetic Gaussian Schell-model (EGSM) beam after propagating through a polarization grating is derived with the help of a tensor method. The statistics properties, particularly the degree of polarization, polarization ellipse and Stokes parameters, of the EGSM beam on propagation after passing through a polarization grating are studied numerically. Our results clearly show that the statistics properties of the EGSM beam on propagation are closely determined by the initial parameters of the EGSM beam and the parameter of the polarization grating. The polarization grating provides one way for modulating the polarization properties of an EGSM beam.     

Investigation of the near field distribution in circular nanostructures using Stokes polarization states

In this paper, the near field distribution patterns formed from nanostripe corral and half spiral are investigated. Various near field distribution patterns are generated owning to the interference of propagating surface plasmon waves that emerged from the nanoslits or nanostripe. The half spiral nanoslits are illuminated with Stokes polarizations. Each polarization state shows a different field pattern at different locations on the surface of metal film. This is due to the excitation of surface plasmon waves at different parts of the nanostructures when illuminated with different types of polarization states. The same Stokes polarization states are also illuminated on a nanostripe corral structure. In this case, dipolar field distributions are observed when illuminated with different linear polarization states, while optical vortices are observed for circular polarization. It is believed that these interesting field patterns due to different arrangements of nanostructures could be used for near field imaging and polarization sensing.