Two-layer dielectric grating for polarization-selective beam splitter with improved efficiency and bandwidth

The polarization-selective beam splitter grating can be widely used in numerous optical information processing systems, which have been investigated for single-layer grating etched in fused silica. The efficiency and incident bandwidth can be improved further based on a novel grating structure. A two-layer dielectric grating is described to realize a polarization-selective beam splitter. Modal analysis is applied to such a dielectric grating to evaluate the grating depths of two layers roughly and accurate grating depths are optimized using rigorous coupled-wave analysis (RCWA). From the optimized results, efficiency can reach 98.9% for TE polarization, which can be improved greatly compared with the reported polarization-selective beam splitter. And efficiency higher than 95% for TE polarization and efficiency ratio of the -1st order to the 0th order varying less than 5% for TM polarization can be obtained within the wide incident wavelength range and angular bandwidth. The improved high efficiency and wideband properties should be attractive for a two-layer dielectric grating as a polarization-selective beam splitter.