层状钙钛矿型Sm2-2xSr1+2x-2yCa2yMn2O7(x=0.2，0.3，0.4，0.5；y=0，0.2，0.3)的溶胶凝胶合成及电性能研究

Layered perovskite manganites with a nominal chemsitry of Sm_2-2xSr_1+2x-2_yCa_2yMn₂O₇(x=0.2, 0.3, 0.4, 0.5; y=0, 0.2, 0.3) were prepared using sol-gel method. The crystal structures of these compounds were studied by X-ray diffraction (XRD) and FTIR absorption spectra. The absorption peaks become weaker and move a little to higher frequency with increasing of Sm/Sr concentration. As the Sm doping increases to x=0.2 and x=0.3, the absorption peaks show a cubic structure character, reflecting that the samples suffer from a transition from tetragonal structure to cubic structure. This coincides with the X-ray diffraction results. The high temperature electrical properties were studied by conventional four-probe method. Although all samples exhibit the semiconductive behavior, lnρ-1 000/T curves are not linear and they obey the small polaron hopping mechanism. Moreover, the resistivity decreases with x reducing. This is due to that Sm doping increases the Jahn-Teller ion Mn³⁺/Mn⁴⁺ ratio, and decreases the e_g bandwidth.     

匹配光纤光栅温度传感解调系统

实验了一种基于一维调节器的光纤光栅静态温度(温度缓变)探测系统。在系统中,一维调节器与步进电机相连,步进电机由PC(计算机)通过PLC(可编程逻辑控制器)进行控制,匹配光纤光栅被固定在一维调节器上用来解调增敏光纤光栅传感器探测到的温度信号,匹配光栅的Bragg周期可通过调节一维调节器进行控制,其透射的光信号经光电检测电路检测并与调节架形成闭环控制。实验测得,在10℃~70℃范围内系统温度传感探测精度为±0.3℃。     

Diode-Pumped Passively Q-Switched Yb：YAG Microchip Laser with a GaAs as Saturable Absorber

A passively Q-switched Yb: YAG microchip laser has been constructed by using a doped GaAs as the saturable absorber as well as the output coupler. At 13.5 W of pump power the device produces high-quality 3.4μJ 52ns pulses at 1030nm with a pulse repetition rate of 7.8 kHz in a TEM00-mode.     

氧化锌微米花的共振拉曼和“负热淬灭”效应

利用化学气相沉积(CVD)的方法通过热氧化高纯锌粉在硅衬底上得到氧化锌微米花. X射线衍射(XRD)结果表明，其具有六角纤锌矿晶体结构.场发射扫描电子显微镜(FE-SEM)图像表明，合成的样品是由很多长且直的ZnO亚微米棒组成的微米花， 具有六角棱柱端面，棒的长度在30μm到50μm之间.在背向共振拉曼散射光谱测量中，观测到ZnO A₁(LO)的五阶声子紫外共振拉曼散射，表明样品具有较高的晶体质量.在变温光致发光谱测量中，观察到明显的中性受主束缚激子(A⁰X)的 关键词： ZnO微米花 光致发光 共振拉曼 “负热淬灭”效应     

Laser Performance of Nd：GGG Operating at 938 nm

We report an efficient diode-pumped Nd-doped Gadolinium gailium garnet （GGG） continuous-wave （CW） laser operating at 938nm. Laser action of 1.6at.% Nd-doped GGG crystais with different lengths and temperatures are aiso investigated. The maximum output power of 620mW is obtained at the incident pump power of 5.0 W with a slope efficiency of 15%.     

衍射光栅 集光效率的研究

<正> 集光效率是衍射光栅的重要光谱性能之一,人们利用“闪耀”的方法,即将三角形刻槽的一边垂直于衍射光线(自准式),使得衍射光栅将光能的大部分集中到某一光谱级次的某一波段,其中某一波长是集光的峰值,此波长称为闪耀波长,而相应的衍射角称为闪耀角。我们结合光栅刻划技术,将影响集光效率的因素分为两大类,即刻线沟槽的几何因素和物理因素加以研究。并从惠更斯原理出发,得出复杂槽形的计算方法。     

非相关双束可调谐染料激光器实验研究

本文报道了研制成功的闪光灯泵浦矩形非相关双束可调谐染料激光器,它可同时在两种染料中获得双束激光输出,具有频差大、脉冲同步、无模式竞争等特点。文中给出了装置结构和典型实验结果,并做了简单讨论。 关键词：     

STUDY OF THE FOUR-WAVE MIXING DIFFRACTION EFFICIENCY OF LONGITUDINAL-FIELD MULTIPLE-QUANTUM-WELL PHOTOREFRACTIVE DEVICE GROWN AT LOW TEMPERATURE

We investigate the relationship between the beam intensity and the four-wave mixing diffraction efficiency of longitudinal-field multiple-quantum-well(LMQW) photorefractive device grown at low temperature. The optimum beam intensity is found. We also explain the different mechanisms of the effect of beam intensity on the diffraction efficiency of the LMQW device and the transverse-field MQW device. Some advice on how to improve the diffraction efficiency is given.     

Diode end-pumped self-Q-switched and mode-locked Nd,Cr：YAG /KTP green laser

We first experimentally demonstrate a laser-diode end-pumped self-Q-switched and mode-locked Nd,Cr:YAG green laser with a KTP crystal as the intra-cavity frequency doubler. The device produces an average output power of 680 mW at 532 nm. The corresponding pulse width of the Q-switched envelope of the green laser is 170±20 ns. The mode-locked pulses have a repetition rate of approximately 183 MHz and the average pulse duration is estimated to be around sub-nanosecond. It is found that the intra-cavity frequency doubling greatly improves the modulation depth and stability of the mode-locked pulses within the Q-switched envelope.     

反应溅射沉积技术制备燃料电池催化层的模拟

反应溅射沉积技术(RSDT)可以生成纳米大小的颗粒并有效溅射形成性能稳定的催化层,是一项崭新的催化层制备技术。为从理论上研究RSDT过程的复杂物理化学过程,本文提出了RSDT过程的三维综合数学模型,模型描述了流体流动、热/质传递,并与燃料气的化学反应和液滴的燃烧相耦合。RNGκ-ε模型用于描述湍动燃烧气流,液滴的跟踪和分析在拉格朗日框架下进行,并利用Monte Carlo方法生成了催化层的表面结构。计算结果可以为该技术的优化提供一定的参考。