Two-Layer Dielectric Grating as Two-Port Beam Splitter

A two-port beam splitter is presented to obtain the 50/50 output based on the two-layer grating. The previously reported beam splitter grating can work only at the special prescribed incident angle. The deviation of incident angle introduces the effect on the splitting ratio uniformity. The proposed two-layer beam splitter grating is aimed to obtain the broad incident angular bandwidth. To optimize the beam splitter, a simplified modal method and rigorous coupled-wave analysis are employed to analyze the propagation process and to calculate the efficiency. Based on the optimized grating parameters, the 50/50 output can be obtained with the polarization-independent property. Most importantly, good splitting ratio uniformity can be exhibited within the broad angular bandwidth for both TE and TM polarizations. The polarization-independent property and the broad incident angular bandwidth are significant for practical applications.