中文摘要：

采用非同时打开的信号光和抽运光在光折变材料LiNbO3：Fe晶体中进行耦合，研究两波耦合增益随时间变化的规律．结果表明：光扇效应对LiNbO3：Fe晶体两波耦合动态过程有显著影响．当入射光光强小于光扇效应的阈值时，信号光和抽运光不同时打开的条件下，两光束耦合过程中，能量增益G随辐照时间变化的曲线与两束光同时打开时基本相同；当入射光强大于光扇效应的闽值时，信号光和抽运光打开的顺序和时间间隔△t不同时，光束耦合能量增益G随时间变化不同．由于光扇效应对抽运光的能量散耗，最大能量增益G的值随着△t的增大而减小，而且G达到最大值所用时间随着△t的增大而延长．

英文摘要：

The dynamical process of two-wave coupling in photorefractive LiNbO3： Fe crystal while the signal beam and the pump beam are non-simultaneously opened, and the signal gain as a function of the opening time are studied experimentally. Our results show that the fanning effect which has a threshold effects on the characteristics of two-wave coupling dynamical process in LiNbO3： Fe crystal. When the writing beam intensity is lower than the threshold of fanning effect, there is no difference with signal gain G as the opening time interval At of the signal beam and the pump beam opened. When the writing beam intensity is higher than the threshold of fanning effect, the maximum of signal gain G decrease as the opening time interval At increase, and it need more time for signal gain G to reach maximum. It is the effect of fanning in LiNbO3 ： Fe crystal which consuming part energy of the wring beam, and effects on the coupling dynamical process.