Highly-efficient element and two-port beam splitter of multilayer-based grating

Highly-efficient element and two-port beam splitter are key elements in various optical systems. We describe that such functions can be fulfilled by one multilayer-based grating. Based on the effective indices of the modes excited in the grating region, grating duty cycle and period are chosen so that the design is feasible. Exact grating depth and thickness of the connecting layer are optimized using rigorous coupled-wave analysis (RCWA). The numerical calculation using RCWA coincides well with predictions of modal method. In the novel design, efficiency of TE polarization is improved greatly compared with the reported dual-function element for the transmission structure.