微弱光电信号检测电路设计

光电检测电路的性能对基于激光诊断技术的脉冲爆震发动机多参数测量系统有重要的影响。针对测量系统中光信号的特点,从改善信噪比、提高带宽及稳定性入手,设计了一种宽带低噪声光电信号放大电路,具有电压增益高、上升沿短及噪声低的特点。该电路主要适用于探测快速变化的微弱光,并在某型发动机多参数测量系统中得到了成功应用。     

一种双频激光干涉信号探测器的设计

为了获取高精密双频激光干涉测量中的干涉信号,完成了一种新的光电探测器电路设计。该探测器利用AD645设计了精密低噪声光电转换前置放大器,保证微弱干涉光信号的有效接收;增益可调的主放大器设计保证输出信号足够的动态范围,适应不同类型的干涉信号处理电路,双二次型带通滤波器有效抑制了噪声与温漂。结果表明,研制的光电探测器能完成微弱干涉信号的接收处理,信噪比高、频率稳定、结构简单易实现,可应用于高精密比相计等激光干涉仪信号处理装置。     

应用于自由空间光通信的PIN激光信号阵列接收器

针对目前的自由空间光通信存在空间光-光纤难以 有效耦合这一问题,考虑到空间光耦合进入光纤后需要将光信号转换为电信号才能实现通信 ,为此本 文提出直接将空间光信号转换为电信号的思想,设计了一种应用于空间光通信的PIN光电二 极管阵列接收器,每一个PIN光电二极管可 以独立接收空间激光并将其转换为电信号,多个PIN光电二极管通过串联和并联将电信号汇 合以方便后续信号处理。对这一新的接收器进行理论分析和模拟实验的结果表明,新的接收 器能有效提高空间光的接收效率。     

双频激光干涉仪相位差测量系统的设计

为了实现双频激光干涉仪相位差的测量,设计了一套双频激光干涉信号处理系统。整个系统包括三个部分:光电接收器、模数转换以及数据处理。光电接收器是将干涉系统的双频激光信号接收并转化成电信号,接收器的设计较好地完成了信号的转化和噪声的抑制,A/D转化电路将接收器输出的模拟信号转换成数字序列。数据处理以两重相关方法为理论基础,将测量系统的参考信号移相90°后得到另一路参考信号,再将测量信号分别与两路参考信号作相关运算,使用FPGA完成硬件实现,最后通过数据计算得出相位差信息。     

基于PLC的激光干涉高分辨率位移测量研究

针对当前激光干涉高分辨率位移测量误差大的问题,设计了基于PLC的激光干涉高分辨率位移测量系统。首先接收激光干涉仪发射信号,然后将激光干涉信号进行光电转换,通过可编程逻辑控制得到激光干涉高分辨率位移测量结果,并将结果显示给用户,测试结果表明,本系统的激光干涉高分辨率位移测量精度超过92%,激光干涉高分辨率位移测量灵敏度高,获得理想的测量结果,并且激光干涉高分辨率位移测量结果明显优于其他系统,具有更高的应用价值。     

空间引力波探测中的激光干涉多自由度测量技术

在空天探索领域，空间引力波探测是当前国际研究热点，核心技术是测量相距数百万千米的两测试质量间的平动转动等多个自由度，探测灵敏度需要在1 mHz～1 Hz频段达到～1 pm/Hz^1/2以及～1 nrad/Hz^1/2水平。目前，激光干涉是实现如此远距离的两个物体之间多自由度测量的最精密的手段，本文介绍了面向空间引力波探测的激光外差多自由度超精密测量技术，概述了其光路结构、测量原理、相位信号处理方法，回顾了近三十年国内外相关研究进展，并分析了空间引力波探测中外差干涉测量的噪声源作用机制以及相关研究进展。最后，对激光外差干涉多自由度超精密测量技术的发展趋势和前景作了展望。     

用HgCdTe变容光电二极管探测60千兆赫以上的CO_2连续波激光差拍

已用热载流子二极管、点接触二极管、块状GaAs混频管及约瑟夫逊结探测了微波频率的激光差拍。这里报导用高速HgCdTe光电二极管作微波谐波发生器、下变频器及光外差接收器来探测60千兆赫以     

光电信号接收器尺寸对光学薄膜弱吸收测量的影响

基于表面热透镜技术搭建了光学薄膜弱吸收测量系统,使用不同功率的抽运光辐照样品,并通过光束质量分析仪记录经样品表面反射后的探测光强度的空间分布,以探测光强度最强点所对应的像素坐标为中心两边对称取多个像素点表示不同尺寸的接收器,从而分析不同尺寸光电信号接收器得到的光热信号强度。结果表明,随着接收器尺寸的增加,探测面积覆盖范围超过探测光束峰值区域,得到的光热信号与抽运光功率的比值逐渐偏离线性,从而引入的测量误差也就增大。因此,实际测量中应在保证测量极限的前提下尽量缩小探测器尺寸以提高测量的准确度。     

基于全光纤激光自混合干涉技术的石英玻璃热光系数测量北大核心CSCD

石英玻璃被广泛运用于航空航天、医学探测、光学成像等方面的光学仪器中,其光学性能是仪器设计时必须考虑的关键因素之一。热光系数作为重要的光学性能参数,其改变会影响光学元件成像的质量以及探测精度,因此石英玻璃热光系数的精确测量对仪器设计及校准十分必要。本文以单模无源石英光纤作为测量对象,提出一种基于全光纤激光自混合干涉技术的石英玻璃热光系数测量方法。实验将纯石英单模光纤作为干涉系统外腔,与光纤激光器熔接,构成全光纤封闭式激光自混合干涉热光系数测量系统。通过高温加热箱给定固定温度范围,利用干涉条纹计数法对石英玻璃热光系数进行解算。实验结果表明,系统对热光系数的分辨率可达到1.6329×10^(-7)/(0.1℃)。此研究结果为进一步开展石英玻璃热光系数的测量以及光纤激光器的自混合干涉应用研究奠定了基础。     

硅PIN光电二极管

本所已于1977年研制出用于红外、激光测距、激光通信等多方面用途的光探测接收器件——0.9微米和1.06微米高速PIN硅光电二极管(两个品种各四个系列),并已定型生产。经二十多个单位试用,证明性能良好:响应速度快,灵敏度高,暗电流小。用户均感满意。硅PIN光电二极管各系列的技术参数如下表所示:     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.