Broadband high-efficiency polarization-independent double-layer slanted grating for RGB colors

A broadband high-efficiency polarization-independent double-layer slanted grating for RGB colors is presented in this paper. The double-layer transmission grating with a graded refractive index is designed by rigorous coupled-wave analysis (RCWA) and simulated annealing (SA) algorithm. The diffraction efficiency of the-1st order can reach more than 84% within the wavelength range from 454 nm to 630 nm under normal incidence. In addition, the diffraction efficiencies of center wavelength for RGB colors (blue:460 nm, green:526 nm, red:620 nm) all exceed 85%, and even hit to 95.6% for TM polarization of green light. Therefore, the proposed double-layer slanted grating has potential value for applications associated with three-dimensional display technology, such as virtual-reality (VR) and augmented-reality (AR) display.