Design and realization of phase retardation-control polarization controllers based on artificial birefringence

Polarization controllers(PCs) are indispensable passive components for state of polarization(SOP) control in optical fiber communication systems.In order to overcome the disadvantages of existing polarization controller(PC),a novel PC based on the artificial birefringence is designed in this paper.The PC results from the concatenation of 3 phase retardation control units each of which consists of two polarization beam splitters,two prisms and one piezoz-lectric transducer(PZT) piezoelectric ceramic.The experimental results show that the proposed PC can convert an arbitrary input SOP to any expected output one with high accuracy under low control voltage.     

Polarization Scattering Property of Cascaded Polarization Controllers

The relation between the allowed range of variation of polarization controller wave‐plates angles and the respective polarization scattering properties is investigated. It is demonstrated that a nearly uniform polarization scattering over the Poincaré sphere is obtained using a concatenation of three polarization controllers with angles randomly changed between ‐π/4 and π/4. It is also shown that an improvement of the scattering properties is obtained if the configuration angles are allowed to change between ‐π/2 and π/2.     

A Miniaturized and Polarization Independent Electromagnetic Shield for C and X-Band Applications

This paper proposes a miniaturized, polarization independent and dual band frequency selective surface (FSS) based electromagnetic shield. A corrugated FSS and zigzag square ring (ZSR) are arranged in back-to-back configuration over single-layered low-profile dielectric. This configuration not only offers shielding for both C and X-band but also achieves stable polarization independent response for these bands. Simulated and measured results verify its 30 dB average shielding over a wide band and 60° polarization independency alongside. More importantly, the equivalent circuit model analysis and analytical parameterization of this dual band configuration is also investigated. The modelling and simulations are in line with measurements that makes it as a potential shield for C and X-band wireless applications including SATCOMs, Microwave filters and many others.

     

Polarization dependence of phase-conjugate reflectivities in solidfilms containing randomly oriented saturable dyes

The properties of polarization-dependent phase-conjugate (PC) reflectivities by degenerate four-wave mixing in saturable-dye-doped films are investigated on the basis of a four-level model including an excited-state absorption. Numerical calculations are carried out by taking account of the effect of molecular orientation as well as of pump propagation under the assumption that optically anisotropic dye molecules are rigidly fixed in a solid matrix without any positional and orientational order, in which a PC wave can be generated even in the case of a probe wave perpendicularly polarized to pump waves. Two cases of the polarization state are employed, where the polarization direction of the probe wave is either parallel or perpendicular to that of the parallel linearly polarized pump waves. Numerically calculating the PC reflectivities as a function of the pump intensity, we show how the polarization properties of the PC-reflectivity curves depend on saturation parameters, and clarify the influences of the molecular orientational and the pump propagation effect. The numerical results are compared with the experimental results obtained by using eosin-Y-doped polyvinyl alcohol films as saturable absorbers     

一维光子晶体偏振滤波器通道数的影响因素研究

光子晶体偏振滤波器是利用光子晶体带隙特性来控制信号光偏振状态的一种新型滤波器, 在光纤通信、光学传感测量、光学信息处理等领域均有重要应用。通道数多少是偏振滤波器设计的重要指标, 通道越多则信息容量越大, 越有利于系统的小型化微型化。利用光学传输矩阵法研究了影响一维光子晶体偏振滤波器通道数目的因素, 研究表明：(1）光子晶体缺陷层厚度是影响滤波器通道数目的关键因素, 通道数N与厚度D近似满足线性关系, 在500 ～650 nm波段函数关系为N=0.0035D+0.159; (2）缺陷层折射率nc的变化也会导致通道数改变, 折射率越大通道数越多;( 3）光子晶体单元层数和单元厚度改变不会影响滤波通道数, 但可以调节通道中心波长位置, 同时对偏振度和分离度也有影响。     

相干光通信中的偏振问题

在相干光通信等方面，要求信号光与本地振荡光偏振方向相匹配，这就要求对偏振进行控制。本文介绍了至今国外出现的有关偏振问题的四类解决方案，重点介绍了其中的偏振控制器原理，最后对各种偏振解决方案作了比较并指出了应用前景。     

电控晶体偏振控制器分析与研究

介绍电控晶体偏振控制器（PC）的内部结构，理论分析了电控晶体PC对偏振态的控制作用，设计并进行了实验，并将理论结果与实验所得的轨迹进行对比和分析，得出了电控晶体PC的波片上所加电压与其对光波偏振态的控制的一些关系。     

Polarization recovery for Polarization Shift Keying transmission based on analysis of torsion and curvature of three dimensional curve segments

A solution to the problem of recovering and tracking the signal configuration at the receiver side for digital optical transmission systems employing the modulation of polarization (POLSK) is proposed. The tracking algorithm for signal configuration is based on analysis of torsion and curvature of three dimensional curve segments. Impact of polarization effects on presented method is investigated. The only impairments considered in this paper are: frequency-independent birefringence and one lumped PDL element. The numerical simulations and experiments shows that the presented method is resistant to change of fiber optics birefringence; and is sensitive to depolarization effect and state of polarization location fluctuations which are equal or faster than the data rate.     

Comments on “Polarization effect on four-wave mixingefficiency in a single-mode fiber”

Dr. K. Inoue, in ibid., vol. 28, no. 4, p. 883, 1992, calculated the polarization properties of four-wave mixing in a low-birefringent fiber by treating the fiber as a random concatenation of M pieces of polarization-maintaining fiber. Though the final result is very elegant, his derivation is rather lengthy. We present a short derivation of his equation by considering the evolution of polarization in low-birefringent fiber as a diffusion process, and calculating the probability density function of the Jones matrix for the first time     

基于波长扫描调制法测量保偏光纤的偏振特性

分析了保偏光纤偏振特性及其拍长和偏振消光比的基本测量原理,并根据单模保偏光纤基模的2个正交偏振模分量HEx11与HEy11间的相位差与波长的关系,推导出偏振拍长的测量关系式,提出了测量保偏光纤偏振特性的波长扫描调制法.采用此方法对熊猫型保偏光纤(YOFC-3367WY)的偏振特性进行了验证性实验研究.拍长和偏振消光比的测量结果表明,在该保偏光纤工作波长处试验结果与理论分析相当一致,说明该方法具有简单易行、测量精度高的优点.     

Polarization Extraction in Planar Near-Field Phaseless Measurements

Near-field measurements typically require both amplitude and phase information to correctly predict the far-field. Unfortunately, there are situations in which the phase data is not available or impractical to obtain. That is why there has been a need for the development of phaseless techniques. Up until now, a number of remarkable solutions to this problem have been proposed by the researcher in different disciplines. Unfortunately, the complete vectorial representation of the field is not investigated in depth. The evaluated cases are usually linearly polarized and only the dominant polarization is investigated while the cross polarized field is usually neglected. This paper addresses the polarization issue in a two-component approach and then proposes a solution to the problem. A searching mechanism, for the incorporation of an appropriate initial guess, is integrated into the well-known, iterative Fourier technique (plane-to-plane) to enhance the algorithm response. Then, using two sets of measured orthogonal information data gathered by two linearly and orthogonally polarized probes, it is shown that with the aid of only a single point amplitude measurement, the polarization characteristics of the antenna can be extracted up to an inherent ambiguity of the right- and left-handedness. In order to have an assessment of the applicability of the proposed method, both linearly and circularly polarized antennas are simulated. Additionally, the method of extracting the polarization from the phaseless data is also verified through a bi-polar near-field measurement.     

Polarization transformation of a wave field propagating in ananisotropic medium

The momentous experimental discovery of the Faraday (1846) effect is sketched from a historical perspective, through the eyes of several well-known scientists. This effect and its generalization can be explained theoretically by using the dispersion theory for waves propagating in an anisotropic medium. A wave of arbitrary initial polarization will have its wave polarization transformed continuously as it propagates. It is convenient to represent this continuous polarization transformation by a locus in the polarization-ratio plane. In a lossless medium, when both characteristic waves are propagating, this locus is a circle. Five cases in a magneto-ionic medium have been investigated for different propagation angles. The results are discussed and illustrated     

偏振模色散及偏振相关损耗对光传输链路相关特性的影响

在同时考虑偏振模色散(PMD)及偏振相关损耗(PDL)情况下，分别通过理论和蒙特一卡罗方法研究了光传输链路的输出信号偏振态相关函数。首先，从理论上得到了光传输链路的输出信号偏振态相关函数的解析表达式，而后，利用蒙特一卡罗方法进行了模拟研究，理论和模拟的结果能很好地吻合。研究结果表明，当光传输链路的偏振模色散值不变时，随着传输链路偏振相关损耗的增大，输出偏振态归一化自相关函数的线宽变宽；而在光传输链路的偏振相关损耗一定的情况下，随着光传输链路的偏振模色散的增大输出偏振态归一化自相关函数的线宽变窄。     

Polarization Effects of GaN and AlGaN: Polarization Bound Charge,Band Bending,and Electronic Surface States

GaN-based devices are currently limited by reliability issues such as gate leakage and current collapse, where the mechanisms responsible for degradation are closely related to the electronic surface state configuration. Therefore, understanding the electronic surface state configuration of GaN-based materials will help improve device performance. Since GaN has an inherent polarization, these materials are also subject to a bound polarization charge, which influences the electronic state configuration. In this study, the surface band bending of N-face GaN, Ga-face GaN, and Ga-face AlGaN was measured with x-ray photoemission spectroscopy after various cleaning steps to investigate the effects of the polarization. Despite the different surface bound charge on these materials, similar band bending was observed regardless of the magnitude or direction of the charge. Specifically, the band bending varied from ?0.1 eV to 0.9 eV on these samples, which supported the models of a Fermi level pinning state at ～0.4 eV to 0.8 eV below the conduction band. Based on available literature, we suggest this pinning state is indirectly evident of a nitrogen vacancy or gallium-dangling bond.     

机械调整式极化跟踪器

在低剖面动中通天线系统中,辐射器多为平板阵列或柱形抛物面的形式,由于天线高度限制,无法通过旋转天线面板的方式进行极化跟踪,需要独立的极化跟踪调整机构,针对此提出了一种新型机械调整式极化跟踪器,具有结构紧凑和可靠性高的特点。通过电机驱动波导关节及OMT实现上行极化调整。基于极化波合成的工作原理,提出了系统设计方案,并描述了核心器件的设计方法。给出仿真与实测结果,且二者吻合较好。     

一种宽带高性能可变极化跟踪器

变极化跟踪装置是动中通卫星通信天线系统关键设备之一。采用阶梯形脊和对称转门结正交模式转换结构设计了一种用于极化跟踪天线的快捷可变极化宽带高性能极化跟踪器,实现了射频信号两个正交极化分量的实时跟踪、分离和提取功能。电磁仿真和优化结果表明,设计的极化跟踪器具有宽频带和高极化隔离性能,在Ku频段大于2 GHz频带内,极化隔离度优于-34.7 d B,端口反射损耗≤-22 d B。     

云母波片偏光干涉谱随温度变化的漂移

为了研究云母波片的偏振参量受温度影响的情况,测量了不同温度下云母波片的偏光干涉谱。利用岛津UV-3101PC分光光度计,在其样品室中加入温控装置,改变波片的温度,对80μm,227.5μm,300μm和813.5μm 4个不同厚度的云母波片进行测量,结果发现,当温度升高时,波片的偏光干涉谱整体向短波长方向发生漂移,且温度变化越大,漂移越明显,这是由波片的厚度和双折射率受温度影响而引起的。结果表明,漂移的偏光干涉谱对于研究云母波片具有精确、直观、简单的优点,这为研究云母波片的偏振参量随温度的变化提供了方法。     

Realization of an Ultracompact Low-Loss Photonic Crystal Corner Mirror

We report on the realization and characterization of an ultracompact, low-loss, and broadband corner mirror based on photonic crystals (PCs). By modifying the boundary layers of the PC region, extra losses of dB per corner mirror are achieved for transverse-electronic polarization for silicon-on-insulator ridge waveguides fabricated by electron beam lithography and inductively coupled plasma etching. Dimensions of the PC corner mirror are less than, which are only about one tenth of conventional waveguide corner mirrors.     

Polarization dragging in injected lasers

The vectorial injection locking of a slave laser by a linearly polarized master laser is theoretically and experimentally investigated, taking the nature and the stability of the eigenstates of the slave laser into account. It is proved that the behavior of the polarization, intensity, and frequency of the slave laser can be described by four nonlinear coupled differential equations, for lasers in which population inversion remains quite constant. In particular, it is shown that the stability of the eigenstates of the slave laser plays a dramatic role in the response of this laser to injection. Isotropic slave lasers are shown to follow adiabatically the polarization of the master laser in the frequency locking range. Loss anisotropic slave lasers exhibit a specific Adler tongue behavior and can support the transfer of the polarization of the master laser only along their eigenstates. Phase anisotropic slave lasers are shown to exhibit two bistable or simultaneous Adler curves and to offer new possibilities of all-optical command. In all of these cases, a good agreement is obtained between theory and experiment and the study of polarization throws light on the physics of injection locking     

Polarization stabilizer using liquid crystal rotatable waveplates

In standard single-mode fiber (SMF) transmission systems, a polarization stabilizer is useful for optimizing the performance of polarization dependent systems or devices. We have proposed and developed a polarization stabilizer which employs liquid crystal (LC) rotatable waveplates. It has a simple configuration, no moving parts, and endless-control characteristic. High polarization stability was confirmed under various state of polarization (SOP) fluctuations. The maximum response speed of the polarization stabilizer is about 900°/s, but this can be increased by improving the controller. We applied the polarization stabilizer to a semiconductor optical amplifier (SOA) having polarization dependence, and achieved good gain stabilization