Hg_(0.8)Cd_(0.2)Te晶体电学参数反常的检测和分析

系统地分析和研究了N型Hg_(0.8)Cd_(0.2)Te晶体电学参数的各种表现,从中归纳出三种霍耳参数反常的Hg_(0.8)Cd_(0.2)Te材料及其霍耳参数随温度和磁场变化的特征。通过实验和理论分析找出这三类材料电参数反常的起因,给出了正确判断材料性能及获取真实反映材料电学特性参数的方法。     

KGd（WO4）2为基质的激光晶体被动锁模研究现状及前景

本文讨论了大功率飞秒激光器对增盆介质的要求,根据各种KGW为基质的激光材料的光谱学以及热学参数,重点分析了KGW激光晶体在获得大功率飞秒脉冲上的优势,给出了采用此类材料进行锁模实验与半导体可饱和吸收镜之间的关系。同时通过对目前KGW的飞秒实验报道的综述,探讨丁影响此类材料飞秒锁模的一些关键因素,综述了以KGW为基质的激光晶体被动锁模的大功率激光器的研究进展与发展潜力。     

InSb晶体生长固液界面控制技术研究

在固液界面控制方面,对Si等成熟半导体的研究较多,而对锑化铟(InSb)材料的研究极少。对InSb晶体等径段生长过程中晶体拉速、转速和坩埚转速对固液界面形状的影响进行了模拟分析以及实际的晶体生长实验。结果表明,这三个生长参数对固液界面形状的平稳控制具有一定的效果。获得了平稳固液界面控制方法,为后续生长更低位错密度、更均匀径向电学参数分布的InSb材料打下了基础。     

KDP晶体激光预处理参数的优化

KDP 晶体是目前高功率激光装置中倍频材料的首选,元件上架前通常采用激光预处理来提高抗激光损伤性能,由于预处理流程耗时较多,提升预处理效率对于工程应用具有重要意义。研究了激光预处理参数对 KDP 晶体材料损伤性能的影响,通过分析激光辐照通量、辐照发次、能量台阶等预处理参数与元件损伤性能的变化关系,发现在一定通量范围内用不同的能量台阶可以获得同样的预处理效果,由此确定采用变能量台阶的方法对预处理参数进行优化。实验证明,采用此方法可以在保证预处理效果的前提下,将总的激光辐照发次缩减三分之一,结果对于大口径 KDP 晶体元件的激光预处理工艺具有重要参考价值。     

激光晶体的键合条件研究

键合晶体作为激光工作物质,可以有效地控制热负载,减小端面的变形和损伤,降低光束的波前畸变。基于键合面缝隙闭合理论,分析了激光晶体的键合条件,计算了Nd∶YAG、Nd∶YVO4和蓝宝石晶体在光胶时键合面处的哈梅克常数和表面能,讨论了这三种材料在制作键合晶体时需要满足的条件,对比了制作的难易程度。以YAGNd∶YAG晶体为例进行了光胶实验,验证了键合条件的合理性;对热处理后的YAG-Nd∶YAG键合晶体进行抽运光照射实验,证明了键合强度和键合稳定性满足实验要求。提出的晶体键合条件判断方法可以为键合晶体的选材和键合工艺的参数优化提供参考。     

Nd3+:Gd3Ga5O12单晶的能级和晶体场计算

测试了Nd3+:GGG单晶在可见和近红外波段的吸收光谱,并分析指认了它的实验能级,通过从头计算的DV-Xa方法计算得到了它的晶体场参数和旋轨耦合参数。用Nd3+:GGG在77K和300K的156个、88个实验能级,拟合了它的自由离子参数和晶体场参数,均方根误差（即拟合精度）σ分别为15.79和 11.48 cm-1。结果表明晶体场参数的拟合结果和从头计算值符合的很好。最后比较了拟合得到的Nd3+:GGG和已报道Nd3+:YAG 的自由离子参数和晶体场参数。     

HgCdTe晶体的缺陷吸除效应

利用二次离子质谱测量HgCdTe晶体杂质时发现:杂质在晶片表面附近有富集现象,实验证明该现象属缺陷吸除效应,分析了杂质富集的机理,并利用缺陷吸除工艺成功地减少了HgCdTe晶体内剩余杂质,低温电学参数、光学透过率测量结果表明:该工艺能提高HeCdTe材料的光、电性能。     

石英晶体激光切割的几点规律

本文基于石英晶体激光切割的参数模型,分析了对激光器功率、切割速度、材料厚度以及切缝宽度的相互关系,研究了石英晶体激光切割过程的基本规律,这为提高激光切割效率、保证激光切割石英晶体的加工精度奠定理论基础,同时也为激光切割石英晶体参数的选择提供了依据。     

Everson腐蚀剂在表征碲锌镉材料位错中的应用

位错密度是晶体材料的重要参数之一，碲锌镉晶体位错研究也一直是红外焦平面研究领域热点之一。由于外延材料对衬底晶向的要求，Everson腐蚀剂在表征位错密度参数方面得到了非常重要的应用，利用Everson腐蚀剂做的位错研究也取得了很多新成果。     

用静态升华法制备CdSe单晶及其性质的观测

本文报道了用改进了的Pirper-Polich方法制备大尺寸优质CdSe单晶,并对晶体的完整性进行了观测,测量了晶体的电学参数、禁带宽度.这些结果表明,采用这种方法制备Ⅱ-Ⅵ族化合物半导体材料,设备简单,生长温度低,实验条件容易控制,有利于得到大尺寸、低位错密度的单晶体,是一种很有前途的方法.     

Intensity Dependence of Stationary Energy Transfer in Codirectional Photorefractive Two－wave Mixing

ＩｎｔｅｎｓｉｔｙＤｅｐｅｎｄｅｎｃｅｏｆＳｔａｔｉｏｎａｒｙＥｎｅｒｇｙＴｒａｎｓｆｅｒｉｎＣｏｄｉｒｅｃｔｉｏｎａｌＰｈｏｔｏｒｅｆｒａｃｔｉｖｅＴｗｏ－ｗａｖｅＭｉｘｉｎｇ￥ＬＩＵＪｉｎｓｏｎｇ；ＬＩＡＮＧＣｈａｎｇｈｏｎｇ（ＸｉｄｉａｎＵｎｉ...     

Intensity Dependence of Stationary Energy Transfer in Codirectional Photorefractive Two—wave Mixing

The intensity and phase formulas that are valid for the saturation and inter-mediate regime(before saturation)are derived,and the analytical expressions with the ration of saturation intensity to total incident intensity as their explicit variable are obtanied.The intensity depenence of stationary energy transfer in photorefractive acodirectional two-wave mixing is examined.It is necessary to using these formulas in some problems,such as the temperature of intensity dependence of two-wave mixing.A method of measuring exponen-tial gain coefficient is presented,which is suitable for two-wave mixing in intermediate regime.     

Polarization properties of enhanced self-diffraction in sillenite crystals

Doppler-enhanced self-diffraction in two-beam coupling experiments with sillenite crystals exhibits pronounced optical polarization effects due to the concomitant presence of natural optical activity and electric-field-induced linear birefringence. Coupled wave equations that describe the polarization properties, exclusive of self-diffraction effects, have previously been derived for the two principal crystal orientations most commonly used in photorefractive recording. In this paper, the coupled wave equations are combined with a linearized model of the photorefractive recording process (single trap level, single mobile charge species) to analyze the impact of self-diffraction effects on the polarization state evolution. Numerical solutions of these equations yield optimum configurations for enhanced gain and improved image contrast in two-wave mixing with such materials. In addition, inclusion of optical activity in the model emphasizes the contribution of this effect to the apparent reduction of the effective electrooptic coefficient of bismuth silicon oxide crystals.     

载流子浓度对光折变LiNbO3晶体二波耦合增益的影响

根据光折变微观机制和Ｋｕｋｈｔａｒｅｖ带导模型，分析了ＬｉＮｂＯ３晶体二波耦合系数与载流子深度的关系。结果表明二波耦合系数随流子浓度的升高而增大，并逐渐趋于一稳定值。测量了不同Ｃｅ掺杂浓度Ｃｅ：ＬｉＮｂＯ３晶体二波耦合指数增益与载流子浓度的关系，实验结果与理论分析一致。     

掺铜锗酸铋晶体的生长及其光折变性能的研究

本文叙述了掺铜锗酸铋晶体的生长；测试晶体的指数增益系数、衍射效率、相位共轭反射率和响应时间。掺铜锗酸铋晶体的光折变性能比纯锗酸铋提高２～３倍。     

Mg：Fe：LinbO_3晶体光折变增强效应的研究

在铌酸锂晶体中掺ＭｇＯ和Ｆｅ２Ｏ３，生长出Ｍｇ：Ｆｅ：ＬｉＮｂＯ３晶体．由于薄晶片的光爬行效应，晶体的二波耦合指数增益系数高达８０ｃｍ－１，且角度响应范围加宽，响应速度和抗光散射能力都比Ｆｅ：ＬｉＮｂＯ３有较大改善．以Ｍｇ：Ｆｅ：ＬｉＮｂＯ３晶体作光放大器，实现了一次迭代全息关联存储．     

Gain constant of two-wave mixing in periodically poledphotorefractive crystal waveguide

A photorefractive crystal waveguide with its c-axis periodically reversed along the waveguide axis is studied to realize enhanced two-wave mixing. The gain constant of two-wave mixing in the periodically poled photorefractive waveguide is theoretically derived in terms of mode-coupling analysis. It is found that, in BaTiO₃ periodically poled waveguides, the net two-wave mixing gain constant is increased by 1.5 to 5 times over that of conventional waveguides without periodical poling because the largest electrooptic coefficient r₄₂ can be effectively used by appropriately setting the angle between the c- and z-axes. Several types of test BaTiO₃ periodically poled waveguides are successfully fabricated by using the electrical poling technique. Typical lateral dimensions of the waveguides are O.5 to 1 mm, and the lengths are several millimetres. The measured two-wave mixing gain constants of the fabricated waveguides are well predicted by the theory     

Effect of the nonlinear saturation of the gain on the peak modulation frequency in lasers based on self-assembled quantum dots

Peak modulation frequency of lasers based on self-organized quantum dots is calculated taking into account the effect of nonlinear gain saturation. Because of a large nonlinear gain coefficient and a reduction in the differential gain with increasing optical losses, the peak modulation frequency is attained for an optimum loss level that is significantly lower than the saturated optical gain in the active region. For lasers based on multiply stacked arrays of quantum dots, the peak modulation frequency first increases with increasing number of quantum-dot layers before leveling off, with the limiting value being inversely proportional to the nonlinear gain coefficient.     

匹配高斯光束在中心对称光折变晶体中的自偏转

通过数值模拟的方法,研究了有外加电场的中心对称光折变晶体中匹配高斯光束的动态演化及自偏转特性.结果表明,对于给定的与中心对称光折变晶体参量匹配的高斯光束,在晶体中能演化为稳定的孤子波;考虑扩散效应之后,匹配高斯光束的中心将发生自偏转.随着入射光强的增加,高斯光束中心的自偏转程度先增加后减小,转折处的入射光强度对应于最窄...     

匹配高斯光束在双光子光折变介质中的自偏转

为了研究有外加电场的双光子光折变介质中匹配高斯光束的动态演化及自偏转特性,采用数值模拟的方法,给出了匹配高斯光束在晶体中的动态演化及自偏转图形。结果表明,对于给定的与双光子光折变介质参量匹配的高斯光束,在介质中能演化为稳定的孤子波;考虑扩散效应之后,匹配高斯光束的光束中心将发生自偏转;随着外加电场的增加,高斯光束的自偏转程度增加,当外加电场达到一定强度后,高斯光束的自偏转程度随着外加电场的增加反而减小;高斯光束的自偏转程度随着入射光强的变化关系与外加电场的情况相似。