CH4受激拉曼散射产生紫外激光用于NO2差分吸收激光雷达的研究

脉冲Nd:YAG三倍频激光(355 nm)泵浦CH4的受激拉曼散射第一级斯托克斯光(395.6 nm)用作NO2差分吸收激光雷达的λon.为研究CH4的受激拉曼散射效应和定量解释其物理机理作了数值模拟计算,并作了一系列的实验.通过调节泵浦能量、光束质量和气体压强,得到了各级散射光的能量转化效率与三者间的函数关系,找到了第一级斯托克斯光的优化条件.     

高纯度高转换效率一阶斯托克斯激光谐振腔研究

正在斯托克斯位移过程中,当有一阶斯托克斯光子产生后,若入射光子的密度足够高,即可产生二阶甚至高阶斯托克斯光子。若入射光子密度相对较低,不能产生二阶斯托克斯过程,则一阶斯托克斯过程的转换效率也很低。因此,很难实现高效并且纯净的一阶斯托克斯光输出。给出了一种采用偏振耦合输入的拉曼激光谐振腔的实验研究结果。该腔在有效抑制二级斯托克斯光产生的同时,实现了高效的一阶斯托克斯激光输出。采用的斯托克斯谐振腔的泵浦激光源波长532 nm,脉宽10 nm,脉冲重复频率30 kHz、该532 nm激光是由波长为1064 nm的二极管泵浦Q开关激光通过LBO晶体倍频得到。在通过b-cut的KGW(KGD(WO_4)2)晶体后,得到的一阶斯托克斯激光波长为559 nm,二阶斯托克斯激光波长为589 nm。为实现上述高纯度高转换效率的559 nm激光输出,一种逻辑上较为简单的方法是采用HR532 nmAR589 nm,且对559 nm有较高反射率的输出腔镜。但由于三个波长间距较小,要实现这样的腔镜镀膜比较困难,且价格不菲。采用泵浦光偏振耦合输入斯托克斯激光腔的方法,即将线偏振的532 nm激光通过α-BBO晶体走离进入斯托克斯腔内的振荡激光光路、腔内加入一片对532nm和589 nm光为半波片,对559 nm光为全波片的特殊波片、从而实现只有559 nm的一阶斯托克斯光可以在谐振腔内多次振荡,而532 nm的泵浦光和589 nm的二级斯托克斯光则在小于等于一次腔内往返光程时即通过α-BBO晶体走离而离开该谐振腔,造成远大于其腔内增益的损耗。基于以上偏振耦合输入斯托克斯谐振腔设计,实现了6.2 W的纯净559 nn激光输出、入射激光至一阶斯托克斯输出激光的能量转换效率达39%、在输出激光中,泵浦光能量与一阶斯托克斯激光能量之比小于0、7%,二阶及高阶斯托克斯激光与一阶斯托克斯激光能量之比小于0.1%、     

BaWO4晶体的高效受激拉曼散射

采用腔外单次通过方式,实现了BaWO4晶体的高效受激拉曼散射(SRS).当抽运光为532 nm皮秒激光脉冲时获得了5级斯托克斯线(559.64 nm,590.26 nm,624.42 nm,662.76 nm,706.18 nm)和3级反斯托克斯线(463.42 nm,484.24 nm,507.04 nm),测量了BaWO4晶体各级拉曼散射谱线的阈值和增益系数,受激拉曼散射的整体转换效率高达78%.当抽运光为355 nm皮秒激光脉冲时观察到3级斯托克斯线(366.52 nm,379.40 nm,393.22 nm),根据一级斯托克斯线的抽运阈值得到相应的拉曼增益为51.8±2.7 cm/GW.实验表明BaWO4晶体具有易生长、透光波段宽、抗光损伤能力强、增益系数大等优点,有望在全波段可见激光的产生方面获得重要应用.     

新型晶体CsLiB6O10倍频转换效率的数值模拟分析

本文首次对调QNd:YAG激光器1064nm光泵浦CLBO晶体的倍频效率与晶体长度和偏振分量比的关系曲线进行了数值模拟计算.若泵浦光采用平面波形,CLBO晶体的Ⅰ类、Ⅱ类SHG效率可超过80％;若泵浦光采用高斯波形,CLBO晶体的Ⅰ类、Ⅱ类倍频效率分别为68.3％和80％。得到CLBO晶体倍频应采取Ⅱ类相位匹配方式的结论。     

用光波导提高拉曼光的转换效率

用波长为1．064μm的Nd：YAG激光器作泵浦源泵浦氢拉曼池，在氢拉曼池中放置充有高压氢气的波导管，观测到波长9．18μm二阶斯托克斯光输出。泵浦能量为25mJ时其输出能量为19．1μJ考虑40％的锗片损耗，二阶斯托克斯光的转换效率为0．13％     

880nm同带泵浦的高效率Nd:YVO4自拉曼激光器

利用880 nm半导体激光器同带泵浦声光调Q Nd:YVO4自拉曼激光器,以减轻热效应对泵浦功率的限制和对拉曼增益的影响,获得高效的1 176 nm一阶斯托克斯光输出。使用两块长度10 mm的Nd:YVO4晶体作为增益介质,脉冲重复频率190 kHz时,在26.8 W入射泵浦功率下获得6.11 W的平均输出功率,光光转换效率22.8%。实验研究了拉曼增益介质长度对输出功率和转换效率的影响,并对自拉曼激光器输出功率曲线中出现凹陷的原因进行分析,认为凹陷并非源自谐振腔稳定性,而是由于增益较弱的斯托克斯光对于谐振腔失调的敏感性所致。对照试验结果显示,与808 nm传统泵浦方式相比,880 nm同带泵浦下自拉曼激光器的输出功率和转换效率得到明显提高。     

可见波段BBO晶体光参量振荡器

本文给出了角度调谐BBO晶体光参量振荡器(OPO)的实验结果。采用ns的Nd:YAG激光的三次谐波355nm作为泵浦源。在λ=650nm处,得到信号波的转换效率为26.6％,连续可调谐输出范围为480～720nm。     

PS光泵高压H_2产生高阶受激喇曼散射

我们利用脉冲Nd:YAG锁模序列激光经过一级放大输出约40mJ的基波光或其倍频光,分别泵浦气压为20kg/cm~2(常温)的氢气喇曼池(H_2的纯度为99.999％),其输出经棱镜分光。结果用0.53μm倍频光泵浦时,仅获得符合正常喇曼频移(4155.2cm~(-1))的三级反斯托克斯光束和一级斯托克斯光束(在319.9nm至683.0nm范围),波长分别为:319.9nm,368.9nm,     

内腔泵浦的BaWO4反斯托克斯拉曼激光器实验研究

实验研究了内腔BaWO4反斯托克斯拉曼激光器的激光特性。通过在调Q的基频谐振腔中插入一倾斜的BaWO4拉曼谐振腔,实现基频光、一阶斯托克斯光和一阶反斯托克斯光的非共线相位匹配,进而实现了内腔反斯托克斯拉曼激光器在968nm的运转。测量了不同泵浦电压下输出的一阶反斯托克斯光的单脉冲能量,当泵浦电压为750V时,获得的最大输出能量为0.79mJ,相应的基频光到一阶反斯托克斯光的转化效率为1.5%。一阶反斯托克斯光的典型脉冲宽度为4.9ns。     

Diode-pumped Yb∶YAG quasi-three level thin-disk laser with 1024 nm output

采用二极管泵浦Yb∶ YAG晶体实现准三能级连续1024 nm薄盘激光器,1024 nm谱线是由Yb∶YAG晶体内的2F5/2-2F7/2能级跃迁实现的,实验中采用折叠腔结构.泵浦光16次通过Yb∶ YAG晶体,当注入泵浦功率为17.9 W时,1024 nm激光输出功率为370 mW,通过采用Ⅰ类临界位相匹配LiB3O5 (LBO)晶体进行腔内二次谐波倍频,获得最大输出功率为45 mW的512 nm蓝-绿激光稳定输出,蓝-绿色激光30 min功率稳定度优于4.3％.     

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.     

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.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.