一种kHz、窄脉宽、高能量激光器的研究

kHz、窄脉宽、高能量的脉冲激光光源在激光测距领域具有广阔的应用前景。依据晶体电光调Q与窄脉宽理论,研究并设计了一种kHz、窄脉宽、高能量调Q的固体激光器。实验采用了一种适用于高占空比、高功率的LD端面泵浦构型,利用三柱透镜耦合系统将泵浦光聚焦至工作物质内,其最大光转化效率能达到27%;分别利用RTP晶体与KD~*P晶体进行高重频电光调Q对比,在近乎相同的静态输入下,KD~*P晶体调Q获得了11 m J的动态能量输出,RTP晶体的动态能量只有5.64 m J。最佳泵浦功率下,KD~*P晶体的动静比接近80%,RTP晶体动静比接近40%。最后,通过改变谐振腔的腔长,验证了短腔法实现窄脉宽激光的可行性,并在物理腔长为60 mm的情况下,获得了5.76 ns的窄脉宽激光。     

914 nm LD泵浦RTP电光调Q的高效率Nd:YVO4激光器

报道了一种激光二极管（LD）端面连续抽运的高重频、高光光效率电光调Q Nd:YVO4激光器。采用RbTiOPO4（RTP）晶体对作为调Q元件,通过减小热效应和模式匹配技术,实现了高效率的高重频窄脉宽1 064 nm脉冲激光输出。一方面采用低吸收系数的914 nm波长抽运Nd:YVO4晶体,使晶体内热分布均匀,从而获得高量子效率的同时减小了热效应影响。另一方面通过优化泵浦光斑半径,实现泵浦光和振荡光好的模式匹配。在重频200 kHz时,获得了最高输出功率16 W,脉宽9 ns,单脉冲能量80 J,光束质量M21.2的稳定脉冲激光,泵浦吸收功率31 W,对应的光光转化效率为51.6%。据笔者所知,这是RTP电光调Q实现的最高效率的脉冲激光器。     

半导体泵浦被动调Q高重频Nd:YAG激光器

从被动调Q固体激光器的速率方程出发,分析给出了Cr4+:YAG被动Q开关Nd:YAG激光脉冲的峰值功率、脉冲能量、脉宽及重频等相关参量表达式.以此为基础,进行了光纤耦合输出的连续半导体激光纵向泵浦被动Q开关Nd:YAG激光器实验研究,采用不同参数Cr4+:YAG晶体作为被动Q开关,获得了不同参数的高重频脉冲激光输出.     

双支路电光Q开关高重频激光器研究

报道了一种采用LD侧面泵浦、双支路电光Q开关实现热退偏补偿的高重频固体激光器。在重复频率1 kHz时,实现了平均功率6.7 W,脉冲宽度16.7 ns的TEM00模激光输出,对千赫兹高重频、窄脉宽、高光束质量激光器的研发具有一定的参考价值。     

自拉曼三阶斯托克斯调Q锁模激光特性研究

报道了一种结构简单紧凑的输出波长为1487 nm的三阶斯托克斯调Q锁模(Simultaneously Q-switched and mode-locked (QML))自拉曼固体激光器。采用光纤耦合输出的大功率半导体激光器单端泵浦掺Nd原子浓度为0.3 at.%的Nd∶YVO4复合晶体,在重复频率(pulse repetition rate (PRF))为25 kHz,泵浦功率为24 W时,输出的波长为1487 nm,获得的最大平均输出功率为588 mW,锁模脉宽为21.09 ps,单脉冲能量为8.23 μJ,峰值功率达到390 kW。     

LD 泵浦高光束质量被动Q 开关激光技术研究

研究了二极管端面泵浦及Cr4 + ∶YAG晶体作为被动Q 开关对激光模式的影响,讨论了二极管端面泵浦的被动Q 开关激光器产生单纵模激光振荡的原因、机理和条件。在实验中,获得了单脉冲能量30μJ ,脉宽6ns ,重复频率2kHz 的单纵模激光输出。     

紧凑型高重频高功率2.06 μm激光器

报道了一种获得紧凑型高重频、高功率2.06 μm激光输出的实验方案并对泵浦过程中脉冲波形稳定性变化进行了简要理论分析。采用794 nm光纤耦合输出Tm∶YAP晶体得到68 W 1.94 μm激光器,其输出激光经光束整形后泵浦Ho∶YLF晶体,并采用声光调Q方式,最终实现平均功率35 W,重频10~15 kHz可调,脉冲波长2.06 μm的激光输出。1.94 μm、2.06 μm谐振腔长度分别为66 mm和90 mm,激光二极管、激光晶体及声光Q开关工作在30 ℃水冷的条件下。方案结构紧凑,热稳定性强,可作为中长波红外光参量激光器小型化有效的泵浦源。     

高重频1.57 μm内腔光学参量振荡器

理论分析了被动调Q固体激光泵浦的光参量振荡器。利用激光二极管泵浦，Cr4+:YAG被动调Q Nd:YAG激光泵浦的内腔光学参量振荡器，磷酸氧钛钾(KTP)晶体作为非线性晶体，获得了高重复频率，高峰值功率的人眼安全激光输出，改变Cr4+:YAG被动调Q晶体的参数，可获得不同重频不同脉宽的调Q激光脉冲；当Cr4+:YAG晶体初始透过率为 T0=80%时，获得了平均功率大于3.8 W，重频约80 kHz的1.572 μm波长信号光输出，脉宽30 ns，脉冲峰值功率达到1.58 kW。     

LD泵浦的YAG热键合调Q激光器

对LD端面泵浦Nd:YAG/Gr4 :YAG热键合调Q激光器进行了实验研究.采用φ3×12mm晶体,端面镀膜方式在晶体两端直接构成平-平谐振腔.采用LD端面泵浦方式,分别研究了该激光器的脉冲重复频率、平均输出功率和脉冲宽度等参数随泵浦功率变化的输出特性,随着泵浦功率的增加,脉冲重复率和输出功率与泵浦功率呈线性增加,而脉冲宽度则有被压缩的趋势.当LD泵浦功率为6W时,热键合调Q激光器获得波长为1064nm、脉宽为5.3ns、平均功率为690mW的被动调Q激光脉冲输出.其光-光转换效率为11.5%,光束发散角为3.1mrad.实验结果表明,热键合激光器热效应好、可靠性高、输出光束质量高,是一种性能良好的新型一体化调Q固体激光器.     

LD端面泵浦Nd∶YVO4/YVO4键合晶体声光调Q激光脉宽研究

利用半导体激光器(LD)端面泵浦YVO4/Nd∶YVO4键合晶体,实现声光调Q 1064nm的窄脉宽激光输出。从理论和实验上分析了泵浦功率和重复频率对输出调Q脉宽的影响。在泵浦功率为20W情况下,重复频率为2kHz时,获得最短脉冲宽度为16.4ns;重复频率为40kHz时,获得了最大平均输出功率为6.9W,光-光转换效率为34.5％。     

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.