利用达曼光栅灰度图去除零级光干扰

Removal of Zero-Order Beam Interference using Dammann Grating Grayscale Map

液晶空间光调制器(LCSLM)加载计算全息图实现激光分束时,会在焦平面处产生零级光干扰,为了解决这一情况,提出一种加载达曼光栅灰度图至液晶空间光调制器的方法,利用相消干涉,从而消除零级光干扰。基于模拟退火算法,求解出相位转折点集,在VirtualLab中进行仿真模拟,利用MATLAB软件编写生成达曼光栅灰度图的脚本文件,搭建基于硅基液晶空间光调制器(LCOSSLM)的验证系统,对调制效果进行测验。结果表明:通过加载达曼光栅灰度图进行激光分束,在CCD视场内明显去除了零级光干扰,且实际分束效果与仿真模拟结果相近,在一维五分束下的分束均匀度达97.190%,优于GSW算法生成的光栅形式全息图的调制效果。以大光点间距进行一维二、七分束的效果观测,分束均匀度分别达98.453%、96.820%,又进行二维分束观测,测量分束均匀度可达95.436%,且均未在CCD视场内观测到零级光。

Zero-order beam interference is generated at the focal plane when the liquid crystal spatial light modulator(LCSLM)is loaded with a computer-generated hologram(CGH)during laser beam splitting.To address this issue,we proposed to load a Dammann grating grayscale map to LCSLM using phase extinction interference,thereby removing zero-order beam interference.Based on the simulated annealing algorithm,the set of phase turning points was solved;simulations were performed in VirtualLab;and a script for generating Dammann grating grayscale maps was written using MATLAB software.Consequently,a verification system was built based on a liquid crystal on silicon spatial light modulator(LCOSSLM),and its modulation effect was tested.The results show that the zero-order beam interference is removed in the CCD field of view by loading the Dammann grating grayscale map for laser beam splitting.Moreover,the actual beam-splitting effect is close to that observed in the simulation results.Furthermore,the beam-splitting uniformity under one-dimensional five-beam splitting reaches 97.190%,which is better than the modulation effect of the grating CGH generated by the GSW algorithm.When the focal distance is large,effects of one-dimensional two-and seven-beam splitting are observed with beam-splitting uniformity levels of 98.453%and 96.820%respectively.The two-dimensional beam splitting is also observed with a measured beamsplitting uniformity of 95.436%.In addition,no zero-order beam is observed in the CCD field of view.