High power terahertz pulses generated in intense laser-plasma interactions

Terahertz (THz) radiation has attracted much attention due to its wide potential applications. Though radiation can be generated with various ways, it is still a big challenge to obtain strong tabletop sources. Plasma, with the advantage of no damage limit, is a promising medium to generate strong THz radiation. This review reports recent advances on strong THz radiation generation from low-density gases and high-density solid targets at different laser intensities.     

均匀电荷密度下的磁绝缘理论研究

在平行板磁绝缘传输线中均匀电荷密度下,分别对压力平衡下的修正层流模型和非压力平衡和非层流模型进行了求解,比较了两种理论模型下的结果。分析表明：相对于非层流模型而言,层流模型因未考虑径向速度,其电荷密度偏低,阳极电场、阳极磁场及阳极电流都偏大。此外,粒子模拟结果显示非层流模型具有更高的精度。最后,对压力平衡条件、均匀电荷密度下的层流以及非层流模型,从平行板理论推广到一般构型。     

High power AlGaInP laser diodes with zinc-diffused window mirror structure

The technology of zinc-diffusion to improve catastrophic optical damage (COD) threshold of compressively strained GaInP/AlGaInP quantum well laser diodes has been introduced. After zinc-diffusion, about 20 μm-long region at each facet of laser diode has been formed to serve as the window of the lasing light. As a result, the COD threshold has been significantly improved due to the enlargement of bandgap by the zinc-diffusion induced quantum well intermixing, compared with that of the conventional non-window structure. 40-mW continuous wave output power with the fundamental transverse mode has been realized under room temperature for the 3.5μm-wide ridge waveguide diode. The operation current is 84 mA and the slope efficiency is 0.74 W/A at 40 mW. The lasing wavelength is 656 nm.     

激光散射法识别和检测病毒初探

复杂的病毒很容易发生突变,在测试过程中为了保持一定的环境温度、湿度、气氛以及对于毒性强的病毒,为了确保工作人员的健康和安全,防止交叉感染,采用光纤传感技术是很有意义的。为了达到隔离遥测的目的,本实验采用了非功能型光强调制式光纤传感装置。 光散射法检测病毒是以病毒的理化性质为依据的。光波通过病毒悬浮液介质时,当病毒微粒大小约为入射光波的λ/10～λ/20时,发生瑞利散射,散射光强为     

GaAs-GaAlAs多量子阱结构中热载流子弛豫过程

将微微秒非线性光学相关技术发展成一种新的微微秒时间分辨光谱技术,并用它研究了GaAs-GaAlAs多量子阶结构中非平衡载流子的弛豫过程,讨论了非平衡电子系统能量损耗的机理,给出了电子-声子散射的时间常数。 关键词：     

用穆斯堡尔谱研究Eu2O3在载体表面上的分散度

用穆斯堡尔谱研究了Eu₂O₃在不同载体表面上的分散度。随着铕含量的变化引起的穆斯堡尔参数的差别表明了Eu₂O₃与不同载体之间作用上的差别。在γ-Al₂O₃表面上,当Eu含量增加时,用质异能位移增加,逐渐接近于体相Eu₂O₃相应值,说明在逐步形成Eu₂O₃晶相。与此不同,在两种SiO_关键词：     

4.2K注氮Ga_(1-x)Al_xAs(x=0.2-0.8)的光致发光研究

本文通过光致发光手段研究了4.2K下Ga_(1-x)AlxAs中等电子杂质氮的发光行为.利用离子注入及适当退火在 Ga_(1-x)AlxAs中获得约 10~(18)/cm~3的氮浓度.实验观察到由于注氮在X导带极小值下面形成的等电子束缚态相关的氮发射带及其声子边带.在4.2K下观察到随退火温度上升及氮浓度增加形成的氮峰增长.测定了氮能级位置随铝组分x的变化关系.同时测量了不同组分原始样品的带边峰位置,初步确定了4.2K下带边能量随组分x变化的经验公式.利用两能谷近似计算了氮束缚能级的位置,理论与实验有较好的符合.对比GaAs_(1-x)Px:N的结果,对由于电负性差异和晶格畸变而引起的氮等电子杂质势随x的变化作了讨论.     

脉冲磁体中的热效应

本文第一次建立了在一个正弦型脉冲通过磁体期间考虑热效应时的瞬态电流方程.计算出热效应引起电流峰值的减小,指出在脉冲时间大于10ms、磁场强度小于1MG的脉冲磁体中,热效应不是影响获得高强脉冲磁场的主要因素,只要解决磁体受力问题,目前的场值还可以大幅度提高;并指出磁体的起始电阻是影响场值的敏感因素. 理论计算第一次给出了在一个脉冲期间,通过磁体的电流与时间关系,及磁体材料的电阻和温度随时间的变化.     

High Coupling Efficiency Generation in Water Confined Laser Plasma Propulsion

High coupling efficiency generation in water confined laser plasma propulsion is investigated. It is found that the coupling efficiency is enhanced over thirty times in water confined ablation compared to that of direct ablation. From calculation of the ablation pressure induced by the plasma on the target surface, it is realized that high coupling efficiency is attributed to the confinement of the water layer on the plasma expansion.