不同夹持方式下不同高反膜系腔镜的热形变分析

在研究高功率激光辐照下激光器腔镜表面热形变分布时通常会忽略其表面镀有的高反射膜系。利用有限元分析软件ANSYS比较了特定激光辐照(吸收功率250W,外环半径4 cm、内环半径2 cm的同轴环形光束,30s)下的高反腔镜在不同夹持方式下的热形变分布,同时考虑了腔镜表面镀有的两种不同高反膜系及膜系中的驻波场的影响,并与通常忽略膜系的情况进行了对比分析。研究表明,采用压圈法时,三种情况下热形变分布的差异相对较小;采用压板法时,三者形变分布产生了明显的差异,镜面中心可能上凸、下凹或者平缓;采用三点法时,尽管镜面中心热形变分布较为平缓,但在环状光束辐照区域内三者仍有明显差异。因此,膜系内驻波场对腔镜热形变分布的影响不能轻易忽略。     

基于变形镜热形变预估模型的自校正效果分析

在波前校正过程中,变形镜(DM)在强激光连续辐照(CW)下会产生热形变,进而对入射光引入附加波前畸变,从而制约了变形镜的波前校正效果,致使光束质量改善效果变差。从变形镜热形变面形的Zernike多项式分解出发,建立了强激光连续辐照下变形镜的热形变预估模型,根据预估所得的热形变面形,模拟计算得到了变形镜的驱动器控制信号参数,进而驱动变形镜对其自身的热形变面形进行了实时补偿。仿真结果表明,该自校正方法能有效补偿变形镜自身的热形变面形,减小变形镜热形变对其校正能力的影响;采用局部换热方式只能在一定程度上减小变形镜形变面形引起的平移相差和离焦相差,对光束质量的改善效果也比较有限,而该自校正方法能有效减小热形变引起的光程差,从而对光束质量起到明显的改善作用。     

熔融石英基片热形变及其对光束质量的影响分析

熔融石英基片受高能激光辐照后，受热产生的热形变会恶化系统出射的光束质量。为了研究光束质量的恶化情况，采用COMSOL有限元分析软件，建立了在连续高能激光辐照下熔融石英基片热形变分析模型，并针对基片在不同的夹持方式下的热形变进行了比较分析，得到了基片受热后的温度分布和形变分布情况，并利用VirtualLab软件定量分析了熔融石英基片热形变对光束质量的影响。结果表明，采用四周固定的方式，热形变量是最小的；基片的热形变会对光束质量造成影响，激光辐照时间越长，热形变量越大，对光束质量影响越大；当基片被激光辐照20s后，采用夹板固定的基片最大形变量达到415.90nm，光束质量因子M_x2由1.0036恶化至1.4571；采用四周固定的基片最大形变量达到98.38nm，光束质量因子M_x2由1.0036恶化至1.0064。这一结果对后续激光合束系统搭建以及光束质量优化有重要的指导意义。     

非垂直入射HS传感器测量数据的修正

采用变形镜模拟激光镜面热畸变,使变形镜在不同的驱动电压下产生相应的形变,用Hartmann-Shack传感器作为测量仪器,分别以垂直入射法和非垂直入射法测量了变形镜在各驱动电压下的形变数据。对比两种方法测得的波前像差峰谷值(PV值)数据发现,非垂直入射法测得的数据小于垂直入射法测得的真实数据,两者之间的相对偏差随形变量的增大而增大,且与入射角密切有关,随着入射角的增大,相对偏差明显增大。若将非垂直入射法测得的数据除以入射角的余弦对数据进行修正,结果与真实数据吻合很好,波前像差PV值最大相对偏差不到2%。     

强激光输出窗口热行为对光束质量的影响

为了研究强激光输出窗口热行为对光束质量的影响,从Strehl比的普遍公式出发,推导出热变形情况下考虑材料折射率温度效应的Strehl比计算公式和远场强度分布公式。计算并分析了蓝宝石、石英、单晶硅组成的窗口镜的热变形对光束质量的影响。激光功率越高,引起的窗口的热变形越显著,使得Strehl比和远场归一化强度越低,因而光束质量越差;在考虑到材料折射率的温度效应时,在相同的激光辐射条件下,蓝宝石的Strehl比随激光功率的变化较平缓。结果表明,高功率激光器的窗口热变形及其基片材料折射率的温度效应对远场光束质量具有较大的影响。     

薄膜残余应力和表面杂质对变形镜疲劳寿命的影响

文中综合考虑变形镜（DM）薄膜残余应力和表面杂质的影响,采用ANSYS有限元分析软件建立了镀高反射膜系的变形镜应力分析模型,进而基于应力-寿命（S-N）曲线和Miner累积损伤理论,分析了波前校正过程中变形镜的疲劳损伤特性,并详细讨论了变形镜薄膜残余应力和不同尺寸的表面杂质对变形镜疲劳寿命的影响。研究结果表明,在热-机械耦合作用下,热效应的存在会加速变形镜的疲劳损伤。对于给定的待校正畸变波前,随着变形镜薄膜残余应力的增大,变形镜承受的动态循环载荷越强,其疲劳寿命越短,且残余应力主要对变形镜镜面疲劳寿命影响较大;而当变形镜薄膜残余应力一定时,畸变波前PV值越大,其表面应力越大,致使疲劳寿命也随之缩短。在强激光连续辐照下,当表面杂质大于一定尺寸时,变形镜疲劳寿命随着杂质粒子尺寸的增大而减小,而当杂质粒子尺寸较小时,则对变形镜的疲劳寿命影响不大。此外,薄膜残余应力的存在将进一步加剧表面杂质对变形镜的疲劳损伤。     

薄膜电极重频电光开关的热管理

透明导电薄膜作电极的普克尔盒电光开关是新一代重频激光驱动系统的理想单元。高重频会在电光晶体内产生热沉积,引起弹光效应,热光效应和晶体形变,使透射光束的波前产生畸变。针对能量千焦耳级,重复频率16 Hz率的激光系统,对薄膜电极普克尔盒采用液冷技术进行热管理;建立普克尔盒的热分析模型,利用有限元算法,分别研究晶体厚度和换热系数对波前畸变的影响,得到晶体厚度的最优值。并模拟了开关晶体上的温度分布、应力分布和机械形变,分析热光效应、机械形变和弹光效应对光束波前和退偏损耗的影响,结合波前畸变和退偏损耗的要求得到优化的参数。     

反射镜热畸变对激光光束质量影响的研究

基于热传导理论,建立了高斯光束辐照硅反射镜的物理模型,利用多物理场数值分析软件COMSOL Multiphysics求解热传导方程,仿真计算得到镜面表面温度分布曲线以及镜面变形曲线,进一步结合光学仿真软件模拟计算,研究得到Si反射镜镜面的热畸变对输出光束质量的影响。结果表明：随着激光辐照时间的增大,反射镜热变形越显著,输出光束质量β因子越大,但β值的变化首先较快而后趋于平缓。随着辐照激光功率的增加,反射镜热变形越大,输出光束质量β因子不断增大。     

星载激光通信光学反射镜镜面热变形及其对光学系统影响的研究

在在轨运行的热环境条件下,星载激光通信端机光学反射镜镜面的热变形会对空地激光通信链路性能产生严重影响。本文利用有限元分析软件ANSYS建立了星上激光通信端机光学反射镜的有限元模型,并对镜体在压圈固定方式与压板固定方式下的热变形进行了仿真。利用ZEMAX光学仿真软件就镜面的变形对光学系统产生的影响进行了分析。仿真结果表明,反射镜面的热变形将导致传输光束扩展、波前畸变,这些影响会使探测器接收功率降低,从而恶化空地激光通信链路的性能。因此为了建立稳定高效的空地激光通信链路,必须在镜面材料选择、镜体应力释放方式、镜体大小选择等方面进行合理设计。     

主动冷却式一维变形镜技术研究

根据高能固体板条主振荡功率放大(MOPA)激光放大器系统输出矩形光束在增益介质长度方向波前畸变的特点,针对性地研制了在一维方向上进行波前畸变校正的新型波前校正器,即一维变形镜(DM1D)。通过仿真模型对镜面厚度及粘接面形状等技术参数进行优化,设计了一个具有11通道的主动冷却型一维变形镜,全口径静态面形峰谷(PV)值为0.17μm,校正动态范围不小于5μm。采用主动冷却技术,使镜面在8 k W/cm2功率密度激光长时间照射情况下温升小于1℃,保持了强光作用下镜面面形的稳定性。在闭环校正试验中,光束质量β因子均值从8.82提高至4.38,有效地校正了光束波前畸变,验证了该一维变形镜在MOPA激光系统中的实用性。     

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.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.