基于严格耦合波分析方法和模拟退火优化算法,设计了一种在正入射条件下具有宽入射波长和角度范围的偏振无关高效率多层倾斜光栅。为了提高衍射效率和带宽范围,提出了一种折射率渐变的四层三明治光栅结构。基于这种结构,设计了一种可见光波长范围内偏振无关异常反射光栅器件。数值结果表明,正入射下,该光栅具有130 nm(550~680 nm)的波长带宽,在此范围内-1级衍射效率均高于93%,同时偏振相关损耗均小于0.2 dB。此外,这种光栅结构还具有47°(-2°~45°)的入射角度带宽,以及较大的制造容差范围。因此,本文提出的这种多层斜光栅在虚拟现实和增强现实显示系统、基于超表面的器件,特别是可见光波段的超透镜等方面具有潜在的应用价值。

An anomalously reflective polarization-independent high-efficiency multilayer slanted grating with broad spectral and angular bandwidths under normal incidence was designed by rigorous coupled wave analysis and using a simulated annealing algorithm. To enhance the efficiency and broaden the bandwidth, a four-layer sandwiched structure with a gradually changing refractive index was proposed. Based on the proposed structure, we designed a polarization-independent anomalously reflective grating structure in the visible band. It exhibits a spectral bandwidth of 130 nm (550--680 nm) with -1st efficiencies higher than 93% and polarization-dependent loss less than 0.2 dB. Moreover, simulation results suggest that the grating structure features an angular bandwidth of 47° (-2°--45°) and large range of fabrication tolerances. Therefore, the proposed multilayer slanted grating will attract great interest for its potential applications in virtual/augmented reality displays and metasurface-based devices, especially for metalenses in the visible range.