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.

本文提出了一种用于RGB颜色的宽带高效偏振无关双层倾斜光栅。通过严格的耦合波分析（RCWA）和模拟退火（SA）算法设计了折射率渐变的双层透射光栅。在法向入射下，在454 nm至630 nm的波长范围内，-1级衍射效率可以达到84％以上。此外，RGB颜色（蓝色：460 nm，绿色：526 nm，红色：620 nm）的中心波长的衍射效率均超过85％，对于绿光的TM偏振甚至达到95.6％。因此，提出的双层倾斜光栅对于与三维显示技术相关的应用具有潜在价值，例如虚拟现实（VR）和增强现实（AR）显示。