A Novel Beamsplitter for Optical Polarization State Interferometry

Abstract

We propose an evanescent-field optical beamsplitter, ideal for experiments in polarization state interferometry. It splits an incident wave into two beams, both being in the same polarization state, related to the incident state by a predetermined SU(2) operation on the Poincaré sphere. The operational characteristics of such beamsplitters are described.     

Polarization Aberration Effects Propagated in Optical Systems

Abstract

The propagation and imaging of polarized light through optical systems described by a polarization aberration expansion is treated by combining a scalar operator calculus with the Jones calculus. The martrix-operator framework provides a means for handling diffraction and propagation in optical systems containing polarization aberrations. An expansion for the polarization aberration function of an optical system, similar to the expansion of the wavefront aberration function into defocus, tilt, piston, and higher-order terms, is analysed. These polarization aberration terms introduce phase changes in the diffraction image proportional to the first and second derivatives of the non-polarization aberrated image structure.     

高能激光光学系统偏振分析

本文详细地论述了反射式激光光学系统偏振态变化的起因。并得到几个重要结论。     

Optical Heterodyne Polarimeter for Studying Space-and Time-dependent State of Polarization of Light

Abstract

This paper describes an optical heterodyne polarimeter with a photodetector array by which the space- and time-dependent state of polarization (SOP) of light can be determined. Since no optical components for polarization control are used, the time response of the polarimeter is free from such components, but is basically limited to the frequency bandwidth of the photodetector array used. The signal and local oscillator beams are coherently photomixed to generate a beat photocurrent at every pixel of the photodetector array. The orthogonal linearly polarized two-frequency components of the local oscillator beam are superimposed with their respective counterpart orthogonally decomposed components of the elliptically polarized signal beam. The generated beat-photocurrent offers the significant physical parameters required for the determination of the space- and time-dependent SOP. The performance principle of the polarimeter is explained and confirmed experimentally.     

非线性系统的有限时间扩张状态观测器的设计

针对非线性系统的不确定项和外部干扰问题,提出了一种有限时间扩张状态观测器的设计方案,实现了非线性系统不确定项和外部干扰的有限时间估计。与传统的线性扩张状态观测器相比,有限时间扩张状态观测器基于终端滑模的思想而设计,其非线性项的引入保障了扩张状态的有限时间估计,进而辅助设计控制器,可以提高系统的鲁棒性能。利用Lyapunov有限时间稳定性理论得到该观测误差系统收敛的充分条件。最后,实例仿真进一步验证了该策略的有效性。     

压电陶瓷的极化反转过程

利用阻抗分析仪和重复迭代法，对Ｐｂ（Ｍｇ１／３Ｎｂ２／３）０．１２５Ｔｉ０．４２Ｚｒ０．４５５Ｏ３压电陶瓷的极化反转过程进行了研究。实验数据显示出了铁电畴随电场变化的整个开关过程，发现极化反转前后压电性有着明显的不对称性，这一异常现象是和场诱应变、电滞回线数所相互对应的。经比较研究后认为，影响极化反转前后压电对称性的机理是空间电荷在晶粒表面积聚形成内偏置电场，由此建立的理论模型可以作出合理的解释。     

Negative-Positive versus Reversal Systems

After a quantitative comparison of the negative-positive and reversal systems in black-and-white as well as in colour photography, the relative merits of each system are evaluated as to their application in various domains. While it seems that the motion picture field, which aims at broad diffusion such as in theatres or in teaching, is best served by a negative-positive system, all uses where the film is rather a recording medium or an intermediate, as in scientific uses or in television, seem rather to require a reversal system. In still photography a reversal taking system with reversal prints has recently gained some appeal, while the negative-positive system seems intrinsically to be the adequate medium for the professional field. The present situation in this domain is still the reverse: amateurs use a bigger part of negative-positive materials, while professional colour photography is widely covered by reversal films.     

铁电体极化反转临界条件的细观力学分析

本文根据经典形核理论,对铁电体极化反转过程的临界条件进行了热力学研究,建立了包括温度影响、外场作用、界面能以及退极化能等的热-力-电耦合细观力学模型,计算了铁电体BaTiO3极化反转的临界形核半径和临界形核功。结果表明在畴变过程中BaTiO3的临界形核半径和临界形核功都随反向电场的增加而减小,同样电场强度作用下临界形核半径和临界形核功随着温度的升高而减小。     

Computational Time Reversal for NDT Applications Using Experimental Data

A model-based non destructive testing (NDT) method is proposed for damage identification in elastic structures, incorporating computational time reversal (TR) analysis. Identification is performed by advancing elastic wave signals, measured at discrete sensor locations, backward in time. In contrast to a previous study, which was purely numerical and employed only synthesized data, here an experimental system with displacement sensors is used to provide physical measurements at the sensor locations. The performance of the system is demonstrated by considering two problems of a thin metal plate in a plane stress state. The first problem, which represents passive damage identification, consists in finding the location of a small impact region from remote measurements. The second problem is the identification of the location of a square hole in the plate. The difficulties one encounters in applying this identification method and ways to overcome them are described. It is concluded that while this is a viable model-based identification method, which may lead, after further development, to a practical NDT procedure, one must be careful when drawing conclusions about its performance based solely on numerical experiments with synthesized data.     

单模光纤偏振状态在线控制器

研制了一种单模光纤偏振状态在线控制器,通过线性双折射和圆形双折射改变单模光纤中光的偏振状态,实验结果与理论分析一致     

Conditions for the Physical Realizability of Polarization Matrices Characterizing Passive Systems

Abstract

We derive conditions for the physical realizability of polarization matrices characterizing passive systems or scattering media. By physically realizable, we mean that 0  g  1 where g ≡ (output intensity/input intensity). Using the singular-value decomposition of an arbitrary 2 × 2 complex-valued matrix, we prove that a Jones matrix T _J is physically realizable if 0  det T _J ⁺ T _J  1. Consequently singular Jones matrices (i.e. det T _J = 0) completely extinguish the output intensity irrespective of the input intensity because g ≡ 0. Corresponding results are obtained for Mueller-Jones matrices (the 4 × 4 real-valued matrices which are the four-dimensional representations of the two-dimensional 2 × 2 complex-valued Jones matrices). We also study the problem for general Mueller matrices; however because of their phenomenological character they do not admit of such criteria as do the Jones and Mueller-Jones matrices. This is because g now depends upon the matrix elements of the Mueller matrix and the input Stokes parameters; whereas for the Jones and Mueller-Jones matrices, g only depends upon the matrix elements. Finally we study the problem of relating the input and output mean randomness.     

Search for Time Reversal Violating Effects: R-Correlation Measurement in Neutron Decay

An experiment aiming at the simultaneous determination of both transversal polarization components of electrons emitted in the decay of free neutrons begins data taking using the polarized cold neutron beam (FUNSPIN) from the Swiss Neutron Spallation Source (SINQ) at the Paul-Scherrer Institute, Villigen. A non-zero value of R due to the e⁻ polarization component, which is perpendicular to the plane spanned by the spin of the decaying neutron and the electron momentum, would signal a violation of time reversal symmetry and thus physics beyond the Standard Model. Present status of the project and the results from analysis of the first data sample will be discussed.     

Glare in Optical Systems for Thermal Band Imaging

Glare is a well-known effect which reduces image contrast and creates false images in optical systems. It is a particularly serious problem in night-vision optics that use image-intensifiers, and this has led to an interest in the glare properties of thermal-imaging systems for night-vision applications. In this paper the causes of glare—multiple reflections, surface and bulk scattering from the optical components, reflections from the inside of the lens barrel and thermal emission from heated parts of the imaging system—are analysed and are shown not to be a significant limitation on the performance of present-day thermal-imaging systems operating at background levels comparable with those at the Earth's surface.     

Optical Communication Systems

Thermal lensing of the active medium inside a laser resonator leads to a dependence of the beam divergence on the optical pumping power. Two effects influence the multimode divergence: the fundamental mode divergence θ ₀ and the mode order m. By using a suitable resonator set-up the variations of the two quantities with pumping power can be arranged to offset each other so that the resultant beam divergence remains constant. When the condition for insensitivity is derived the resulting constant divergence is found to be θ _ma = R/d _i, where R is the radius of the limiting aperture of the active medium, and d _i is the distance from the mirror S_i to the principal plane of the active medium. Experiments with Nd-YAG/glass lasers have confirmed these theoretical results.