陷光探测器偏振响应特性的研究

偏振响应特性是反映光探测器质量的重要参数。陷光探测器(陷光二极管)是低温辐射计的传递探测器。中对陷光探测器的偏振响应特性进行了测量研究，并提出了对它的数值表述方法。探测器偏振响应特性的测量结果的不确定度达到0．005％。测量结果表明，不同的反射型陷光探测器的偏振响应特性相差很大，在光辐射测量中不容忽视。     

KDP晶体光学均匀性检测实验研究

本文阐述了正交偏振干涉测量技术的基本原理和实验方法.Fizeau干涉仪的输出激光束经过线偏振镜后变为线偏振光,调整偏振方向让光束的偏振态分别平行于KDP晶体的o轴和e轴,得到两幅干涉图.通过这两幅干涉图的差值得到晶体的折射率分布不均匀性.该检测技术借助可改变输出激光偏振态的大口径干涉仪精确地测量晶体在切割方向上.光折射率和e光折射率的偏差.本文所采取的方法是在大口径干涉仪的小端口放入可改变偏振方向的线偏光镜.本文通过对一批330mm×330mm的大口径KDP晶体的折射率均匀性测量验证了该方法.     

光照度计偏振特性的实验研究

介绍了光源偏振度的测量和消偏振的方法以及照度计偏振误差的概念。测量了实验室用三支灯的偏振度及两台照度计的偏振误差。测量结果表明，光源偏振度均小于１０％，当光垂直入射时对照度计的影响是非常小的。     

具有光弹性敏感元件的光学压力传感器

1.前言人们认为光弹性方法是分析应力的最满意的方法之一。该方法采用了一台测偏振的传感器,也可用于压力测量,具有较好的温度稳定性。测偏振的光学传感器采用了单模激光二极管作光源和一台全光纤光学干涉仪,在力和压力测量应用中得到了证实。结果说明,装置的灵敏度不受环境温度变化的影响。然而,干涉     

光栅分振幅光偏振测量系统的研制

使用一个既能产生反射光衍射又能产生透射光衍射的特殊金属光栅作为分光器,研制一种新颖的高速光波偏振态测量系统。它没有使用转动光学部件或调制器,而是将金属光栅产生的四条1级衍射光的光强线性地转换为电信号,通过定标方法得到系统的非奇异的仪器矩阵,然后通过线性运算得到入射光的待测Stokes矢量。该系统结构紧凑、安装方便,可用作实时偏振测量术和椭偏测量术中的偏振态探测器。     

光纤型偏振OCT系统中光偏振特性的研究

建立了偏振光在生物组织中传播的模型,并利用该模型模拟了偏振光在生物组织中传播的过程,重建了多种偏振态输入光的情况下光偏振态在生物组织中的分布及生物组织的偏振特性模型.分析了光偏振度与光被生物组织散射次数的关系,阐明了由于偏振光在组织中传播,其偏振态逐渐改变而造成的偏振OCT 干涉计两臂光束失去相干性及偏振OCT 图像质量下降现象.通过分析斯托克斯(Stokes)矢量和穆勒(Muller)矩阵在光纤型偏振OCT系统中的应用,说明Muller 矩阵不受输入光偏振态的影响,因此它比Stokes 矢量更适用于光纤型偏振OCT 系统研究.     

中国计量院建立70GHz光探测器时间响应测量装置

正本刊讯日前,中国计量科学研究院自主建立的70GHz光探测器时间响应测量装置顺利通过专家验收。验收组专家一致认为,在国内首次研制成功的测量装置核心器件———具有标准器属性的70GHz高速光偏振调制器,使我国在高速电光调制器研制方面具有完全自主知识产权;该装置总体技术达到了国际先进水平,为我国     

应用新型磁光调制器的高分辨率偏振消光测量系统

应用新型磁光调制器的高分辨率偏振消光测量系统     

光镊力谱系统双光束串扰因素研究

为了降低和消除光镊力谱系统中双光阱之间的干扰,进一步提高测试精度,本文对双光阱光镊系统中两光束间串扰的成因及其对力谱测量的影响展开了研究.研究发现,高倍物镜组与样品池构成的光学结构会引起光束偏振态的改变,是双光束串扰形成的主要因素;偏振分光棱镜自身的分光特性是串扰产生的另一因素;光阱捕获的微球,虽然改变了光束的形状和传播方向,但在光束串扰方面贡献很小.双光束的串扰信号叠加在探测的光强信号上,影响了光阱刚度和位移灵敏度的标定,最终导致力学测量的偏差.光镊系统中双光束的串扰量在同一次实验的一定时间内基本稳定.根据双光阱光镊系统的这一特点,本文提出了实时测量双光阱光镊系统两光阱独立存在时和同时存在时双光阱的刚度和位移灵敏度的方法,并经多次实验求平均后得到两种情况下双光阱的刚度和位移灵敏度的比值,在后续实验中,将该比值作为修正参数对实测的力谱曲线进行修正.结果表明,该方法有助于减小双光束串扰的影响,优化力谱测量结果,测试精度提高3.4!.     

基于各向异性二维Ge Se的无偏振器偏振图像传感器

偏振是光的一个重要信息,偏振探测可以把信息量从三维(光强、光谱和空间)扩充到七维(光强、光谱、空间、偏振度、光偏振等),为成像物体提供关键的视觉信息(如表面粗糙度、几何形状或方向),因此偏振成像技术在目标检测等领域有着巨大的潜力.然而这些领域往往需要复杂的偏振编码,现有的复杂透镜系统和偏振器限制了集成成像传感器的小型化能力.本文通过二维各向异性α-Ge Se半导体,成功实现了无偏振器的偏振敏感可见-近红外光电探测器/成像仪.作为传感器系统的关键部件,该原型Au/GeSe/Au光电探测器具有灵敏度高、光谱响应宽、响应速度快(~10³A W^-1, 400–1050 nm, 22.7/49.5μs)等优点.此外,该器件在690–1050 nm光谱范围内表现出独特的偏振灵敏度,并且对沿y方向的偏振光吸收最强,这一点通过分析α-Ge Se的光跃迁行为也得到了证实.最后,将2D-Ge Se器件应用到成像系统中进行偏振成像,在808 nm近红外波段处,在不同的偏振方向上,辐射目标的对比度为3.45.这种成像仪在没有偏振器的情况下,能够在场景中感知双频偏振信号,为偏振成像传感器阵列的广泛应用奠定了基础.     

Polarization properties and fractional-power analysis of coated and uncoated parallel-slab multireflection beam splitters

The polarization properties of coated and uncoated parallel-slab multireflection beam splitters are investigated. In a recent study [Opt. Lett. 21, 1709 (1996)] it was shown that the parallel-slab beam splitter is a basic optical component of the parallel-slab division-of-amplitude photopolarimeter. The ellipsometric parameters and the fractional powers for multireflected components generated by this system are analyzed. Interesting new observations with respect to the polarization properties at the Brewster angle of incidence and the distribution of powers among the multireflected components are presented.     

Spectral polarization measurements by use of the grating division-of-amplitude photopolarimeter

The grating division-of-amplitude photopolarimeter (G-DOAP) is an instrument that exploits the multiple-beam-splitting, polarizing, and dispersive properties of diffraction gratings for the time-resolved measurement of the complete state of polarization of collimated broadband incident light, as represented by the four Stokes parameters as a function of wavelength across the spectrum. It is a compact, high-speed sensor that has no moving parts and is simple to install and operate. These characteristics make the G-DOAP well suited for in situ spectroscopic ellipsometry (SE) applications for monitoring and controlling thin-film processes. The design and performance of a prototype instrument are presented. Precise SE measurements, to +/-0.04 degrees in psi and +/-0.1 degrees in delta, are demonstrated in the 550-940-nm wavelength range.     

Mueller-matrix ellipsometry using the division-of-amplitude photopolarimeter: a study of depolarization effects

A fully automated Mueller-matrix ellipsometer with a division-of-amplitude photopolarimeter as the polarization-state detector is described. This device achieves Mueller-matrix ellipsometry by measuring the Stokes parameters of reflected light as a function of the fast axis C of a quarter-wave retarder, which, in combination with a fixed linear polarizer, determines the polarization state of incident light. The reflected Stokes parameters were Fourier analyzed to give the 16 elements of the Mueller matrix. We investigated depolarization of polarized light on reflection from rough, heterogeneous, and anisotropic surfaces by obtaining measurements on rolled aluminum and plant leaves. The results demonstrate (1) a variation of degree of polarization of reflected light with the input polarization state, (2) the precision with which the measured matrices describe the depolarization results, (3) effects of surface anisotropy (rolling direction) on depolarization and cross polarization by reflection from aluminum surfaces, and (4) large values and differences in the depolarization effects from conifer and deciduous leaves. Depolarization of light reflected by the aluminum surfaces was most sensitive to the angle between the plane of incidence and the rolling direction when the incident Stokes parameters S(1), S(2), and S(3) were equal.     

Division-of-amplitude Photopolarimeter (DOAP) for the Simultaneous Measurement of All Four Stokes Parameters of Light

To measure all four Stokes parameters of a light beam simultaneously, the beam is divided into four separate beams using a beamsplitter and two Wollaston prisms. Linear detection of the light fluxes of the four component beams gives four signals that determine the four Stokes parameters. This division-of-amplitude photopolarimeter (DOAP) is completely characterized by a wavelength-dependent 4 2 4 matrix that can be determined directly by calibration. The instrument has a fast response (that is limited only by the photodetectors) as it has no moving parts or modulation.     

Optimal beam splitters for the division-of-amplitude photopolarimeter

Optimal optical parameters of the beam splitter that is used in the division-of-amplitude photopolarimeter are determined. These are (1) 50%-50% split ratio of the all-dielectric beam splitter, (2) differential phase shifts in reflection and transmission delta(r) and delta(t) that differ by +/- pi/2, and (3) ellipsometric parameters (psi(r), psi(t)) = (27.368 degrees, 62.632 degrees) or (62.632 degrees, 27.368 degrees). It is also shown that for any nonabsorbing beam splitter that splits incident unpolarized light equally, the relationship psi(r) + psi(t) = pi/2 is always satisfied.     

Normal Spectral Emissivity of the Industrially Used Alloys NiCr20TiAl,Inconel 718, X2CrNiMo18-14-3, and Another Austenitic Steel at 684.5 nm

Normal spectral emissivity measurements at 684.5 nm for two steels and two nickel-based superalloys at the melting transition and in the molten state are reported in this study. The measurements were performed using a division-of-amplitude photopolarimeter on a microsecond time-scale which is part of a resistive pulse-heating experiment. Emissivity results for the investigated steels do not show any apparent correlation whereas the results for the nickel-based alloys are conclusive and may be used as reference values for similar alloys whenever measurements are too time consuming or not feasible. A weakly increasing emissivity with rising temperature was observed in the liquid state for all the investigated alloys which may be taken into account whenever temperatures are optically measured. However, the measurements presented here show that such a correction does not exceed 0.2 % per 100 K and might only be necessary at a metrological level of accuracy.     

Single-layer-coated beam splitters for the division-of-amplitude photopolarimeter

A design procedure is presented for a near-optimal, single-layer-coated prism beam splitter that serves as the key optical element of the division-of-amplitude photopolarimeter (DOAP). For given film and substrate refractive indices, the angle of incidence and film thickness are selected such that the ellipsometric differential phase shifts in reflection and transmission deltar, and deltat, differ by +/- pi/2, and the normalized determinant of the instrument matrix is maximized. The best results are obtained by using high-index films on low-index substrates. This is illustrated by examples of ZnS and GaP films on silica prisms in the visible and Si, Ge, and PbTe films on Irtran 1 substrates in the infrared. A 16 degrees Si-prism DOAP beam splitter at the 1.55-microm lightwave-communications wavelength is also presented. It uses a 163-nm SiO2 coating on the entrance face to satisfy the optimum delta condition at 73 degrees incidence, and the determinant of the instrument matrix is 78.23% of its theoretical maximum. The exit face of the Si prism is antireflection coated with a 208-nm Si3N4 film.     

Performance optimization and light-beam-deviation analysis of the parallel-slab division-of-amplitude photopolarimeter

A division-of-amplitude photopolarimeter that uses a parallel-slab multiple-reflection beam splitter was described recently [Opt. Lett. 21, 1709 (1996)]. We provide a general analysis and an optimization of a specific design that uses a fused-silica slab that is uniformly coated with a transparent thin film of ZnS on the front surface and with an opaque Ag or Au reflecting layer on the back. Multiple internal reflections within the slab give rise to a set of parallel, equispaced, reflected beams numbered 0, 1, 2, and 3 that are intercepted by photodetectors D(0), D(1), D(2), and D(3), respectively, to produce output electrical signals i(0), i(1), i(2), and i(3), respectively. The instrument matrix A, which relates the output-signal vector I to the input Stokes vector S by I = AS, and its determinant D are analyzed. The instrument matrix A is nonsingular; hence all four Stokes parameters can be measured simultaneously over a broad spectral range (UV-VIS-IR). The optimum film thickness, the optimum angle of incidence, and the effect of light-beam deviation on the measured input Stokes parameters are considered.     

Photopolarimeter based on two gratings recorded in thin organic films

A photopolarimeter based on two different kinds of diffraction gratings (a two-grating photopolarimeter) has been developed for real-time measurements of the four elements of the Stokes vector. The main elements of the device are a pure polarization grating and an ordinary transmission grating, both recorded by means of holographic techniques in thin films of organic materials. The first one consists of a diffraction grating recorded by two interfering opposite circularly polarized beams in a Langmuir-Blodgett film of an azo-compound material. The second component is a grating recorded by two interfering parallel circularly polarized beams in a thin film of a photosensitive polymer. Both gratings offer long time stability and good diffraction efficiency. Four photodiodes collect the first-order diffracted beams from these gratings, the output signals of which are read through an analog-to-digital converter by a PC. The optical alignment of the device is easy and the calibration is realized in a one-step procedure.