非线性光栅的自适应光限幅

首次采用液晶为自聚焦媒质，夹在内表面刻有光栅的两玻璃片间，以Ar离子激光514.5nm波长的激光束垂直入射到光栅上，实验验证了该光栅的自适应光限幅特征。

Adaptive Optical Limiting of Nonlinear Grating

Self focus medium liquid crystal was placed between two BK7 glass plates,and the grating with the triangle groove was caved on the internal surface of one of glass plates for making nonlinear modulation grating.An Ar ion laser beam with 514 5nm wavelength was irradiated perpendicularly to the grating surface and was focused on the liquid crystal.The diffractive angle of the laser beam was depended on the grating period.The intensity of 0 order beam was depended on the depth of the grating groove.Because the liquid crystal is self focus medium,the increasing of laser power density focused on the liquid crystal can change the refractive index difference between the liquid crystal and BK7 glass plate.Under a specified value of the laser power,it was obtained by experiment that the laser power density focused on the liquid crystal was 0 5kW/cm 2,the refractive index difference between the liquid crystal and BK7 glass plate was nearly equal to 0.As a result,the grating in this structure was covered,the various diffracted orders of the transmitting sample almost disappeared,only 0 order beam was left;deviating from this value,the grating reappeared,the various diffracted orders appeared immediately,0 roder beam was weakened.This modulation effect is on physical basis for adaptive optical limiting of the nonlinear grating.The effect of the adaptive optical limiting has the features of large bandwidth and high speed optical limiting.So it has important application prospects in tunable protection of lasers.