分束角度是衍射型激光分束器件重要性能指标之一。目前对大角度衍射分束元件的研究局限于Dammann光栅，Dammann光栅依靠周期内相位突变点对入射光波进行调制，其分束均匀性对突变点精度非常敏感，现有加工技术无法满足设计精度的要求。针对这一问题，提出利用亚波长多台阶结构来实现大角度的激光分束，给出了一个1×16，入射光波长1.55 μm，衍射角29°的16台阶亚波长分束光栅设计实例。设计时利用标量理论获得一个多台阶结构作为初值，经严格耦合波理论结合遗传算法进行矢量优化后衍射效率达到89%，均匀性误差为4.53%。结果表明，亚波长多台阶结构能够实现大角度、高衍射效率以及高均匀性的激光分束。

Splitting angle is one of the significant performance parameters of diffractive laser beam splitter. Current study of wide-angle diffractive beam splitter mainly focuses on Dammann grating. Dammann grating relies on its periodic transition points to modulate the incident optical wave, however the inhomogeneity of outgoing beams is extremely sensitive to the precision of transition points, and the existing processing technology cannot meet the requirement of design accuracy. So, using a sub-wavelength multi-level structure to achieve wide-angle beam splitting is put forward and an actual design example of sub-wavelength 16 levels grating is given, whose incident wavelength is 1.55 μm, beam splitting number is 16 and diffraction angle is 29°. Getting an initial structure by scalar diffraction theory and then applying rigorous coupled- wave analysis and genetic algorithm to do a vector optimization, finally the diffraction efficiency rises to 89%, inhomogeneity drops to 4.53%. The results indicates that sub-wavelength multi-level structure can achieve wide-angle beam splitting with high diffraction efficiency and homogeneity.