一种基于法布里-珀罗干涉仪的位移测量方法

介绍了一种基于法布里-珀罗干涉仪的位移测量方法,为了克服通常的法布里-珀罗干涉仪在位移测量范围方面的局限,采用两束可调激光分别对法布里-珀罗腔的两个相邻谐振峰的光频率进行追踪测量,能够得到任意时刻法布里-珀罗腔的长度,从而实现对测量镜位移的测量,测量范围可以达到毫米量级。对影响测量精度的主要因素进行了简要分析,结果表明采用本方法能够实现纳米级精度位移测量。     

光纤法布里-珀罗传感器的解调方法研究综述

光纤法布里-珀罗传感器以灵敏度高、抗干扰能力强等优点在医疗检测、水声探测、电力监测等领域受到了广泛的关注。光源参数、传感头结构与解调方法是制约光纤法布里-珀罗传感器检测能力的主要因素。对光纤法布里-珀罗传感器解调,即从携带法布里-珀罗传感器腔长信息的输出光信号中提取腔长信息。该腔长信息映射出了传感头所感受到的振动、位移、加速度、温度等待测量信息。一种好的解调方法能够提高光纤法布里珀罗传感器的解调速度、分辨率、动态范围等性能,而光纤法布里-珀罗传感器的解调方法多达数十种,针对特定的应用场景如何选择适宜的解调方法往往令人困扰。本文首先介绍了光纤法布里-珀罗传感器的输出信号特征,然后从原理上详述了常见解调方法的影响因素,并介绍了国内外研究单位提出的多种改进方法,最后从解调方法的适用范围及光纤法布里-珀罗传感器的复用技术两方面出发,提出了解调方法的选取原则。     

基于法布里-珀罗干涉仪的微位移测量方法研究

介绍了一种基于法布里-珀罗干涉仪的微位移测量方法,通过将位移测量转化为频率变化量的测量,实现了亚纳米级测量分辨力.建立了基于法布里-珀罗干涉仪的微位移测量实验装置,完成了320 nm范围内的位移测量,并将测量结果与精密电容传感器的测量结果进行了比较.     

激光双法布里--珀罗干涉纳米测量系统的理论分析

本文设计了一种基于双法布里-珀罗干涉仪、采用计算机实时处理、以轻拍式探针为传感器的新型纳米测量系统,描述了该系统的工作原理,详细进行了系统的理论分析.提出了通过测量双法布里-珀罗干涉仪透射光强基波幅值差或基波等幅值过零时间间隔的方法进行纳米测量的理论基础,分析了轻拍式探针的振动模型,给出了检测探针振幅变化的新方法及理论依据.     

多半波滤光片及其设计

介绍了简单法布里－珀珞滤光片和多半波滤光片的结构和特性，并且对两者的透射率光谱特性进行了比较。分析了多半波滤光片的特点，进行了最优化的膜系设计。文中给出了一种最优化设计的程序流程图。     

适用于微机电系统的自适应红外探测器的可调谐滤光器设计与开发

微机电系统与高品质红外探测技术联合运用为国防、商业、通信、生物医学检测及环境监测等许多应用领域面临的一系列具有挑战性的问题提供了唯一可行的解决方案．可调谐法布里．玻罗滤光片是适用于微机电系统的红外探测器的核心部件．滤光片的结构设计和关键结构件的材料对于滤光片的性能和整个装置的完善性有重要影响．阐述了利用有限元建模进行法布里-玻罗滤光片机械设计和分析的方法．报告了滤光片的结构材料——用低温等离子增强化学沉积法制造的氮化硅的结构表征和机械性能测定方法和结果．最后展示了一些所制作的滤光片阵列．     

光纤压力传感器制作研究

分析了现有光纤压力传感器的原理与结构,选择非本征型法布里-珀罗腔作为研究目标,建立了测压的数学模型,开展了微机电加工工艺研究,探索了包括研磨、腐蚀、减薄与键合等特殊工艺,批量制作的法布里-珀罗腔具有一致性;建立了一套基于机器视觉的测量与焊接系统,能够在线精确测量与焊接控制,实现光纤与准直管的焊接以及准直管与法布里-珀罗腔的焊接。利用本系统,制作出传感器灵敏度为1.765 nm/kPa,在不采用非线性拟合校正的条件下,膜片挠度-压力的线性度为99%,重复性为1%,迟滞为0.7%,温度敏感系数为0.15 nm/℃,零位长时漂移小于2 nm。     

液晶多肽及其应用研究

基于国内外最新研究文献,系统论述了近年来液晶多肽的大分子链结构、液晶性能及应用前景等方面的研究进展。指出液晶多肽在一定条件下将出现各向同性态到各向异性态的可逆转变,伴随着大分子链从线圈状到螺旋状的可逆转变。聚[γ－苄基－L－谷氨酸酯]有序度参数可达0.875。二次谐波的产生证明了有些液晶多肽呈现奇异的胆甾相结构,其胆甾相由极性向列型片晶组成,且分子偶极矩和长轴方向平行。多肽既可显示溶致液晶性又可显示热致液晶性,其液晶相多为胆甾型,有时呈向列型。外加场如取向场及电场对多肽的液晶性也会产生强烈影响。液晶多肽可加工成液晶态水凝胶、纤维和薄膜等,可望用作全息照相材料、光学元件、彩色滤色器以及溶致液晶电池等。     

光纤饱和吸收体稳频窄线宽光纤激光器

结合光纤饱和吸收体与光纤光栅法布里-珀罗标准具,研制出了全光纤结构1550nm单频窄线宽掺铒光纤环形激光器.采用两个976nm激光二极管双向抽运作为抽运源,高掺杂浓度铒光纤作为增益介质,以行波腔消除空间烧孔效应,利用光纤光栅法布里-珀罗标准具窄带选模特性,以10m长低掺铒光纤饱和吸收体稳频,得到了十分稳定的窄线宽激光输出.激光器抽运阈值功率21mW,在抽运光功率为145mW时输出光功率39mW,斜率效率30%,信噪比大于50dB.采用延迟自外差方法精确测量光纤激光器线宽小于10kHz.     

激光双法布里：珀罗干涉纳米测量系统的理论分布

本文设计了一种基于双法布里－珀罗干涉仪、采用计算机实时处理、以轻拍式探针为传感器的新型纳米测量系统，描述了该系统的工作原理，详细进行了系统的理论分析。提出了通过测量双法布里－珀罗干涉仪透射光强基波幅差值差或等幅值过零时间间隔的方法进行纳米测量的理论基础，分析了轻拍式探针的振动模型，给出了检测探针振幅变化的新方法及理论依据。     

Efficient polarization converter for projection displays

In the waveguiding limit, a twisted nematic liquid crystal cell behaves as an achromatic polarization rotator. We propose and demonstrate the application of such a polarization rotator to convert unpolarized light into linearly polarized light with almost 100% efficiency. This polarization converter has a 2:1 aspect ratio, which is close to the 16:9 ratio for modern televisions. It can be used therefore in a projection display with polarization-dependent light valves such as a liquid crystal light valve. Both transmittive and reflective light valves can be used. The temperature dependence of the achromatic polarization rotator is also studied.     

Optimization of the spatial light modulation with twisted nematic liquid crystals by a genetic algorithm

An optimization technique determining the configuration of optical components in a spatial light modulator is proposed. We study a spatial light modulator composed of a twisted nematic liquid crystal, a polarization state generator, and a polarization state detector. To obtain the desired phase and amplitude modulations, four parameters of the polarization state generator and detector should be optimized. A genetic algorithm is applied in searching the configurations suitable to a given twisted nematic liquid crystal. By embodying the proposed technique, the evolution of the designed cost functions is proved.     

Liquid-crystalline polarization converter

A new concept of the polarization converter based on a nematic liquid crystal is proposed for application in an acoustic imaging system.     

Modeling of the diffraction efficiency and polarization sensitivity for a liquid crystal 2D spatial light modulator for reconfigurable beam steering

A nematic liquid crystal spatial light modulator used as a phase-modulating device and operating in the reflective mode is analyzed using three-dimensional modeling. Two configurations, which differ in their electrode placement relative to a fixed quarter-wave plate, are considered across a range of steering directions, with the grating conformal and in some cases oblique to the pixel grid. For each steering direction the sensitivity of the diffraction orders to the polarization state of the incident wavefront is studied. Optimal alignment of the liquid crystal is suggested to reduce this sensitivity.     

Prototype fiber optic liquid crystalline sensor for pressuremonitoring

This paper presents results of initial tests performed on a new prototype fiber optic liquid crystalline sensor for hydrostatic pressure monitoring, which employs pressure-induced deformations in twisted nematic liquid crystal cells. The prototype pressure sensor is based on polarization effects occurring in the reflective configuration of the liquid crystal cells under the Mauguin limit. Results indicate that the prototype sensor offers high response to pressure with reduced temperature sensitivity and, depending on the replaceable liquid crystalline sensing element, can be adjusted for monitoring of low hydrostatic pressures up to 4 MPa     

Photopyroelectric Calorimetry Investigations of 8CB Liquid Crystal–Microemulsion System

In this work, the photopyroelectric technique has been used to investigate the phase transitions in a liquid crystal microemulsion by combining the simultaneous high temperature resolution thermal diffusivity measurements and optical polarization microscopy observations. It has been found that, during the conversion from the isotropic phase into the nematic one, the micelles are expelled from the nematic domains and remain confined in islands of isotropic material which survive down to the smectic temperature range. A hysteresis in the thermal diffusivity profiles between heating and cooling run over the isotropic–nematic transition temperature range has been observed which has been ascribed to the different micelles distribution into the sample volume during cooling and heating runs. Finally, the almost bulk-like behavior of the thermal diffusivity over the nematic–smectic phase transition confirms that a significant fraction of the micelles are expelled during the nucleation of the nematic phase.     

Extended phase modulation depth in twisted nematic liquid crystal displays

We show how the phase modulation depth in twisted nematic liquid crystal displays (TNLCDs) can be increased dramatically by selecting a polarization configuration with a reduced mean intensity transmission. This phenomenon, which we have validated with various devices, is shown here for a device that presents a phase-only modulation only slightly over π radians in our classical rotated eigenvector configuration, but it is capable of producing close to a 2π phase depth for a configuration with 5% mean intensity transmission. A quantitative explanation is presented by means of a phasor analysis of the TNLCD eigenvector projections over input and output polarization states. The proposed technique can be a very useful solution in modern TNLCDs that have a very thin liquid crystal layer and a reduced maximum achievable phase modulation.     

基于偏振分束器的C波段可调谐薄膜滤波器

针对多腔窄带薄膜滤光片在倾斜入射时会产生严重的偏振相关损耗问题,研制了一种基于双折射晶体偏振分束器、信道间隔为100 GHz的角度可调薄膜滤波器.该方法可简化倾斜入射时多腔窄带薄膜滤光片消偏振膜系结构,通过对入射光信号偏振态的控制,仅使用常规窄带滤光片就能实现角度调谐其中心透射波长.该可调谐滤波器件具有结构简单、成本低...     

Observation of the electrostatic defects induced by ionizing radiation in a liquid crystal

Defects generated by a flux of α particles in a nematic liquid crystal (NLC) have been observed in a polarization microscope. The observed objects are treated as electrostatic defects with a dipole character induced in the NLC. This phenomenon can be used for the creation of ionizing radiation detectors.     

Cholesteric Liquid Crystals with a Broad Light Reflection Band

The cholesteric‐liquid‐crystalline structure, which concerns the organization of chromatin, collagen, chitin, or cellulose, is omnipresent in living matter. In technology, it is found in temperature and pressure sensors, supertwisted nematic liquid crystal displays, optical filters, reflective devices, or cosmetics. A cholesteric liquid crystal reflects light because of its helical structure. The reflection is selective – the bandwidth is limited to a few tens of nanometers and the reflectance is equal to at most 50% for unpolarized incident light, which is a consequence of the polarization‐selectivity rule. These limits must be exceeded for innovative applications like polarizer‐free reflective displays, broadband polarizers, optical data storage media, polarization‐independent devices, stealth technologies, or smart switchable reflective windows to control solar light and heat. Novel cholesteric‐liquid‐crystalline architectures with the related fabrication procedures must therefore be developed. This article reviews solutions found in living matter and laboratories to broaden the bandwidth around a central reflection wavelength, do without the polarization‐selectivity rule and go beyond the reflectance limit.