对由两矩形位相光栅构成的双层体积全息光栅的分束特性进行了优化设计，获得了扇出光来数分别为2，3和5，总衍射效率高于89％，光强分布不均匀性小于5％的分束器。

The parameters of several double-layer rectangular phase-only gratings are optimized in order to obtain the beam splitters with high diffraction effieiency and good intensity uniformity. The beam splitters with respectively 2, 3, and 5 fan-out beams and higher than 89% of total diffraction efficiency and less than 5% of intensity nonuniformity are obtained theoretically.