反射型体相位光栅对连续激光光束空间低通滤波

Low-Pass Spatial Filtering for Continuous-Wave Laser Beam by Reflection Volume Phase Gratings

选取4块反射型体相位光栅,两两配对分为两组,各组中的光栅条纹面相互垂直,光栅矢量面正交放置,构成反射型体相位光栅空间低通滤波装置,被用来实现连续激光光束二维空间低通滤波的功能。利用Kogelnik耦合波理论,分析了上述装置对连续激光光束的空间低通滤波性能,并模拟了其对畸变高斯光束的空间低通滤波效果。结果表明,采用这种装置可使得畸变高频角谱成分具有极低的衍射效率,而对有用低频角谱成分具有高达98%以上的衍射效率,能够达到不须对入射光束聚焦就能实现高、低频角谱成分空间分离的目的,从而使得滤波后的光束较未畸变光束的空间光强分布基本一致。

Four pieces of reflection volume phase gratings are selected,and then divided into two groups,in which the fringes are orthogonal to each other.The planes of grating＇s vector of each group are perpendicular to each other.As a result,a two-dimensional low-pass spatial filtering for continuous-wave（CW）laser beam is achieved.Based on Kogelnik＇s coupled-wave theory,the performances of that configuration of filtering for CW laser beam are analyzed,and the filtering characteristics of the configuration for deformed Gaussian laser beam are simulated.The results show that the components with high angular frequency of the input laser beam have lower diffraction efficiency,while those with low angular frequency have higher diffraction efficiency up to 98% in this configuration.The high angular frequency can be filtered out from the laser beams without focusing.The spatial intensity distribution of filtered laser beam is similar to that of undeformed one.