Picosecond Stimulated Raman Scattering of SrWO4 Crystal

Stimulated Raman scattering （SRS） of picosecond pulses is investigated in a new crystal SrWO4. The second harmonic generation of a mode-locked Nd：YAG laser system is used as the pump source. In an external singlepass configuration, the SRS thresholds for the first to the fourth Stokes lines are measured. For the first Stokes line, the steady-state gain coefficient of the SrWO4 crystal is calculated to be 15.96cm//GW. In our experiment, as many as five Stokes lines （559.23 nm, 589.61 nm, 623.49 nm, 661.50 nm, 704.44 nm） and three anti-Stokes lines （506.97nm, 484.34 nm, 463.65nm） are observed, and the total conversion efficiency is as high as 62%.     

可调谐激光晶体S因子和声子能量的估算

本文采用了一种特别的多模电-声子耦合模型,利用室温光谱数据估算可调谐激光晶体的黄昆-里斯(Huang-Rhys)S因子,并与单模耦合模型的结果作了比较.最后,还讨论了S因子与晶场强度及基质晶体价键特性之间的关系.     

Evaluation of Optical Properties of Self-Frequency-Doubling Crystal Yb：GdYAl3（BO3）4 for Laser Applications

Yb：GdYAl3 （B03）4 （Yb：GdYAB） is investigated as a new laser crystal for potential applications in self-frequency doubling. The emission and absorption properties of Yb：GdYAB crystal are studied, and the emission decay times of the upper laser level are measured. The emission cross sections are evaluated using the absorption cross section and principle of reciprocity. The other laser performance parameters, such as the minimum inversion fraction βmin, pump saturation intensity Isat and minimum pump intensity 1rain, are also calculated. The results are discussed in the framework of requirements for an effective diode-pumped Yb^3＋ laser system. Yb：GdYAB is expected to exhibit the most useful laser properties and to be superior to Yb：YAB crystal that has been excellent self-frequency-doubling crystal at present in many key spectroscopic parameter values.     

Fluctuation of Mesoscopic RLC Circuit at Finite Temperature

We consider the fluctuation of mesoscopic RLC circuit at finite temperature since a resistance always produces Joule heat when the circuit is working. By virtue of the thermo field dynamics and the coherent thermo state representation we show that the quantum mechanical zero-point fluctuations of both charge and current increase with the rising temperature and the resistance value.     

具有电容滤波整流线路,二极管断电时间的讨论

席德明先生在物理通报1956年第10期发表的‘关于“二极管和整流作用”的补充’一文中写道“由于C已经被充电至E_m,这时,它将通过负载电阻R_放电”。认为二极管不能通电的时间开始于e_1=e_=E_m即t=π/2时,是错误的。因为二极管断电的时间是t_0(如图1),t_0>π/2。而二极管不通电时的等效电路中C开始放电的电压很明显不是E_m,而是E_0。这是因为输入电压e_1(或e_2)经过E_m后是沿正弦曲线下降的,而电容两端电压e_0达到E_m后是沿指数曲线下降的。后者比前者快,用数学式子比较t=π/2时二者的斜率即知:     

用聚四氟乙烯软带贴面法修复BQ2020六米龙门刨导轨

我厂大型机床BQ2020六米龙门刨床的导轨两次严重拉伤。第一次于1981年2月,拉伤断续总长5.910mm,最宽处20mm,最深处1.35mm。第二次于1983年8月,在其它部位又发生拉伤,断续总长3400mm,最宽处20mm,最深处2mm。两次都用AR-5耐磨胶粘补,并经刮研后使用。但这样严重的拉伤很可能使机床报废,给国家带来重大损失。因此在1984年底对该机床导轨进行了专门修理。     

稀土—铱—锑合金热电材料的结构与量子化学计算研究

应用离散变分Xa量子化学计算方法，研究了IrSb3，Ir4NdGe3Sb9和Ir4SmGe3Sb9三个skutterudites的组成、结构、化学键和热电性能之间的关系。对Ir4NdGe3Sb9和Ir4SmCe3Sb9，用多个模型研究了稀土元素振动的结构。计算结果表明，稀土原子靠近Ge原子的模型比靠近Sb原子的模型更为稳定，热导率也较低。Ir4NdGe3Sb9的共价键比Ir4SmGe3Sb9弱，Ir4NdGe3Sb9和Ir4SmCe3Sb9的共价键又比IrSb3弱，与热导率的实验测量结果一致。     

Bi—2223相高温超导体结晶过程的宏观研究

本根据ＤＴＡ实验测得的降温曲线上的放热峰，探讨了Ｂｉ－２２２３相高温超导体的昌过程及其温度特性曲线，相变的观特征与宏观动力学特征，结果表明，用热分析方法研究高温超导体结晶过程中相变的宏观特征及其规律，对实用化成材的热处理工艺技术有着积极的实践意义。     

金属Bi的卸载熔化实验研究

在火炮上利用金属铋(Bi)直接撞击单晶LiF窗口, 开展了金属Bi反向碰撞的冲击加载-卸载实验研究, 实验采用激光位移干涉测试系统, 获得了金属Bi在11—16 GPa压力范围内完整的卸载粒子速度剖面. 实验结果结合特征线方法计算表明, 金属Bi经冲击加载进入体心立方相, 并在11—16 GPa冲击压力作用下发生了卸载熔化, 界面粒子速度剖面的卸载拐点, 对应着金属Bi经冲击加载后发生的卸载熔化, 而这一结论同Cox的理论计算及一维流体力学程序计算结果基本一致. 本文报道的金属Bi卸载波剖面解读技术, 对于认识冲击加载下其他相似材料相变具有实用价值.