Propagation of reflective three-output with dual-layered grating in second-order Littrow configuration

A novel type of three-output dual-layered reflective grating is proposed in this paper. Through rigorous coupled-wave analysis, the appropriate thickness of two dielectric layers in grating region can be calculated. According to the optimization results, when the incident light with wavelength 1550 nm is incident at the second Bragg angle, the grating can diffract the incident light energy to the three orders, and the efficiency is close to 33%. Compared with the reported three-output grating under the second Bragg angle incidence, the dual-layered grating has higher diffraction efficiency and better incident angle bandwidth for TE-polarized light.