反射式液晶空间光调制器电控光束偏转

Electro-controllable optical beam deflection employing reflective liquid crystal spatial light modulator

为获得较大的光束电控偏转范围,使用空间分辨力高达8μm的反射式液晶空间光调制器实现了对入射632nm激光的电控偏转。利用双光束共焦干涉方法测量了液晶空间光调制器的电控相位延迟特性,最大相移量可达3π。根据二元光学理论和器件的电控相位延迟特性,设计了周期台阶相位模式和相应的加载灰度图,以最大衍射效率实现对入射光束的闪耀电控偏转。结果表明:相位模式台阶数为8时,可以实现10mrad的光束偏转,闪耀级次衍射效率可达46%。利用二元光学的衍射模型对影响衍射效率的关键因素进行了分析,认为器件较低的填充因子和周期台阶模式相位重置点诱导的指向矢回程区是限制光束衍射效率的主要因素。

An electro-controllable spatial light modulator of 8 μm spatial resolution was employed to deflect the 632 nm He-Ne laser beam to high steering angle.The phase shift characteristic of the modulator related to the applied gray level was measured by co-focal interferometry and the maximum phase shift is 3π.According to the principle of binary optics,Different phase models were designed to deflect the incident laser beam.The incident laser beam can be deflected by 10 mrad apart from the incident laser when the phase level is eight,and the diffraction efficiency is high as 46%.The experimental and numerical results indicate that beam deflection with large angle can be achieved by employing the reflective liquid crystal phase-mode spatial light modulator,and the diffraction efficiency is mainly limited by the fill factor and the fly-back region in the liquid crystal cell.