布里渊放大修正陡前沿Stokes脉冲波形

研究了受激布里渊散射(SBS)放大池中．通过改变抽运光与Stokes种子光脉冲的延时．改变它们在池中的相遇位置．实现抽运光对陡前沿种子光脉冲不同部位的选择性放大．从而修正Stokes脉冲波形。理论和实验研究了Stokes光脉宽、脉冲波形前后沿时长比以及能量提取效率等参数随相遇时间的变化规律．在相遇时间2．5ns时，理论得到前后沿时长比为1，能量提取效率80%以上的Stokes放大光脉冲波形．理论和实验符合较好。     

多模石英光纤SBS相位共轭实验研究

采用芯径为100μm、长2m的无掺杂多模阶跃石英光纤,在1.06μm波段,研究了不同焦距下,光纤与耦合透镜间的距离以及泵浦能量对反射率和波形的影响。在不同的入射能量下,得到最大反射率为68.95%,脉宽压缩到入射光脉宽的1/3～1/2。     

多模光纤布里渊散射阈值理论分析与计算

针对目前受激布里渊散射(SBS)阈值研究主要针对单模光纤,而对多模光纤研究较少的现状,理论分析和计算了多模光纤SBS阈值特性。结果表明:对于多模光纤,由于其多个模式的布里渊增益谱叠加导致频谱展宽,其布里渊增益谱最大增益1.667 5×10-11 m/W较单模光纤偏低。根据多模光纤布里渊散射增益,通过SBS阈值公式获得了50/125μm阶跃折射率多模光纤和渐变折射率多模的SBS阈值与光纤长度、衰减系数、纤芯半径之间的关系。理论分析可知,阶跃折射率多模光纤的SBS阈值是渐变折射率多模光纤的4.5倍,更不容易发生SBS非线性效应。     

多模与单模光纤级联系统对激光束的传输

分析了激光束在光纤中的非线性传输损耗,理论上证明了受激布里渊散射(SBS)是光纤传输能力的主要限制因素;实验上在532nm波段对长度为5m,纤芯半径为1.75μm,数值孔径(NA)为0.11的单模光纤的传输能力进行了测定,结果与理论一致。采用模场耦合理论,推导出多模光纤与单模光纤的直接耦合效率表达式,计算得到耦合效率与所选用的多模光纤和单模光纤的纤芯芯径之间的模拟关系。激光器输出波长为532nm;多模光纤的数值孔径为0.11,纤芯半径为12.5μm;单模光纤的数值孔径为0.11,纤芯半径为1.75μm,实验结果与理论基本吻合。根据理论和实验结果,设计出多模光纤与单模光纤混合传输方案,在柔性传输较高激光功率的同时可以得到高光束质量。     

椭圆高斯分布半导体激光器泵浦被动调Q激光器的优化

在考虑泵浦光束和初始反转粒子数椭圆高斯分布的条件下，确定了新的调Q耦合速率方程。在椭圆高斯分布近似下，通过数值分析的方法针对脉冲能量进行优化，首次得到了归一化的脉冲能量和反射镜反射率等关键参数与无量纲变量z的关系曲线。文中以半导体激光器贴近端面泵浦，Cr4+:YAG作为饱和吸收体的Nd:YVO4被动调Q激光器为例进行了脉冲能量优化计算，在小信号透过率为75%，反射率91.8%时，对应最大脉冲能量1.5 J，峰值功率81 W，脉冲宽度18.4 ns。选用小信号透过率为73.4%的饱和吸收体和反射率为87%的反射镜进行实验验证，得到的脉冲能量为1.25 J，峰值功率为76.4 W，脉冲宽度为16.3 ns。理论计算与实验结果基本相符。     

1550nm单频脉冲光纤激光放大器实验研究

为了满足相干探测技术对激光光源的需求,采用主振功率放大技术,对全光纤、高重复频率、1550nm单频脉冲光纤激光器进行了研究.得到了脉冲宽度400ns、重复频率10kHz、单脉冲能量14μJ、平均功率148mW的单模光纤激光脉冲输出.实验中还发现了光纤中过高的功率密度所引起的受激布里渊散射(SBS)将导致激光脉冲波形的变...     

基于阵列透镜和光纤集束的调频脉冲波形测试技术

提出了一种基于阵列透镜和渐变多模光纤集束的调频脉冲测试方法,该方法通过渐变折射率多模光纤提供较大的接收孔径,通过子孔径拼接方式取样降低取样光斑在光纤端面的漂移,两者相结合可实现光束近场能量到光纤集束的高效稳定耦合。该方法中的渐变多模光纤集束可携带更多的取样光能量,有利于脉冲的高对比度测量。实验结果表明,本技术方案能够实现调频脉冲光束整体时间特性的保真测量,测量对比度可达630:1。     

红外纳秒激光脉冲在光纤中传输特性研究

为了提高激光时间波形测量系统的抗干扰能力,建立了激光脉冲在光纤中的传输物理模型,分析了纳秒脉冲在光纤中的线性传输特性,对影响脉冲传输特性的因素进行了系统评价。采用空气与光纤传输进行比对的方法,实验测试了激光脉冲经过不同长度的单模和多模光纤传输后的脉冲波形,得到脉冲展宽在允许的测量误差范围内所需的阈值条件。结果表明,该研究对神光-Ⅲ主机激光脉冲时间波形测量的设计具有重要的意义。     

红外纳秒激光脉冲在光纤中传输特性研究

为了提高激光时间波形测量系统的抗干扰能力,建立了激光脉冲在光纤中的传输物理模型,分析了纳秒脉冲在光纤中的线性传输特性,对影响脉冲传输特性的因素进行了系统评价.采用空气与光纤传输进行比对的方法,实验测试了激光脉冲经过不同长度的单模和多模光纤传输后的脉冲波形,得到脉冲展宽在允许的测量误差范围内所需的阈值条件.结果表明,该研究对神光-Ⅲ主机激光脉冲时间波形测量的设计具有重要的意义.     

Cr4:YAG被动调Q激光器脉冲波形数值模拟及优化

从Nd:YAG晶体Cr4+:YAG被动调Q激光耦合速率方程组出发,数值求解该方程组,获得了激光脉冲的波形。从能量分布和时间分布的角度分析了被动调Q激光脉冲波形的不对称性。定义了描述脉冲波形的对称因子并分析了其与饱和吸收体初始透过率和输出镜反射率的关系。提出了计算脉冲宽度的新方法,重新计算了在脉冲波形非对称条件下的脉冲宽度及其与饱和吸收体初始透过率和输出镜反射率的关系。提出了优化脉冲波形和脉宽的简便方法。     

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.