Transient Response of Photorefractive Grating in BSO and GaP by Short Light Pulse

(1)研究了BSO和GaP晶体的响应时间和衍射效率随折射率光栅间距的变化特性。在被占用受体初始条件下，基于统一带输运模型对数据进行分析，理论与实验结果吻合较好。干涉条纹的特征波数K_O是最重要的参数，因为它不仅表征了衍射效率与K曲线的关系，而且还表征了响应时间与K曲线的关系。根据这些特征估计了这些晶体的一些物理参数。(2)采用新建立的“四能级”模型分析了短光脉冲照射后折射率光栅的时间演化，该模型考虑了导带与一个给体能级、一个电离受体能级和两个浅受体能级之间的载流子动力学。(3)通过测量新开发的光激电流（LSC）、瞬态光电流和热激电流（TSC），研究了BSO和GaP晶体与光折变特性相关的电学特性。利用去除外加电场后形成的内部电场进行TSC测量，在不受噪声电流影响的情况下成功识别了几个深阱。(4)通过监测He-Ne激光束衍射光束强度，研究了短光脉冲照射后BSO晶体的瞬态光折变特性。以前观察到的特殊响应曲线，在第一次快速上升和第二次缓慢上升之间有一个下降，可以用新开发的“四能级”模型来解释，该模型具有两个浅受体水平，一个非活性电离受体水平和一个供体水平。瞬态光折变特性和瞬态光电流的温度依赖性也支持该模型。少

(1) Both response time and diffraction efficiency versus index grating spacing characteristics were examined for BSO and GaP crystals. The agreement between the theory and experiments is quite good, when the data are analyzed on the basis of the unified band transport model under the initial condition of occupied acceptors. The characteristic wave number of the interference fringe, K_O, at which maximum diffraction efficiency can be obtained under steady state condition, is the most important parameter because it characterize not only the diffraction efficiency versus K curve but also the response time versus K curve. Some physical parameters of those crystals were estimated from those characteristics.(2) Time evolution of the index grating after illumination of a short light pulse was analyzed by using a newly developed "Four- Level" model, where carrier dynamics between conduction band and a donor level, an ionized acceptor level and two shallow acceptor levels is considered on the b … More asis of thermally stimulated current (TSC) measurement for trap identification.(3) Electrical properties of BSO and GaP crystals relevant to photorefractive properties were studied by measuring a newly developed light-stimulated current (LSC), transient photocurrent and thermally stimulated current (TSC). The internal electric field formed after removal of external applied electric field was utilized for TSC measurements, where several deep traps were successfully identified without suffering from noise current.(4) Transient photorefractive properties of a BSO crystal after illumination by short light pulses were studied by monitoring diffracted beam intensity of a He-Ne laser beam. Previously observed peculiar response curve, having a dip between first fast rise and second slower rise, can be explained by a newly developed "Four-Level" model with two shallow acceptor levels, an inactive ionized acceptor level, and a donor level. Temperature dependences of transient photorefractive properties and transient photocurrent also support the present model. Less