液晶空间光调制器(LC-SLM)能实现光束动态偏转,而它的像素结构以及相位回卷方法造成的衍射效应使其光效率降低。通过数值仿真和实验分析了像素结构造成的衍射效应,给出了像素填充因子和衍射效率的关系。利用256 pixel×256 pixel的液晶空间光调制器构建动态光束偏转实验装置,使入射光束偏转不同角度时测量远场光斑强度,得到衍射效率随光束偏转角的变化关系。理论分析与实验结果表明,填充比越小,像素结构造成的衍射效应越强,衍射效率降低; 当填充比为0.85时衍射效率的测量值仅为51.3%。相位回卷方法使液晶空间光调制器形成类似闪耀光栅结构,随着光束偏转角度的增大,衍射效率降低。

A liquid-crystal spatial light modulator (LC-SLM) can be used to deflect laser beam, however its pixel structure and diffraction effect resulted from phase wrapping technique decreases its optical efficiency. The diffraction effect was analyzed theoretically and experimentally, and the relationship between fill factor and diffraction efficiency was demonstrated. 256 pixel×256 pixel liquid crystal spatial light modulator was used to alter the wavefront phase to achieve different deflections of a laser beam dynamically. The far field intensity distribution was measured at different deflection angles. The results show the diffraction efficiency decreases with the fill factor. Its measured diffraction efficiency was only 51.3% when the fill factor is 0.85. The phase wrapping technique make the LC-SLM form the structure asablazed grating and its diffraction efficiency decreases with the increase of the deflection angle.