Polarization-independent two-dimensional dielectric grating for 3 × 3 beam splitter

Conventional multi-port beam splitters with spot arrays, while being key components in diversiform optical systems, show polarization sensitivity and insufficient uniformity. Here, we proposed a polarization-independent high-efficiency 3 × 3 beam splitter based on the two-dimensional(2D) cylindrical dielectric grating (CDG), which could redistribute the incident light into nine beams with equal power. The proposed grating consists of a double-layer dielectric cylinder on the substrate of fused silica. The parameters of grating structure and fabrication tolerance are calculated by using rigorous coupled wave analysis (RCWA) and simulated annealing algorithm. The numerical results show that nine diffraction orders ((0, 0), (±1, 0), (0, ±1), (±1, ±1)) have average diffraction efficiencies of 10.12 % with uniformity of 2.8 % and mean polarization-independent loss (PDL) of 0.076 dB for TE and TM polarization. This work can open a new and positive way for researching the 2D multi-spot beam splitter and has promising applications in the field of three-dimensional(3D) imaging and reconstruction, microscopy techniques, material processing, etc.