“…Comparatively, it is easier to be realized by using multilayer gratings. For example, two orthogonal gratings were demonstrated experimentally, and achieved a broad independent polarized bandwidth with a high reflectance (Niraula et al 2016; Broadband reflector based on double-layer subwavelength gratings Qi Wang*, Rui Li, Xufeng Gao, Shuhua Cao, Chunxian Tao, Ruijin Hong, and Dawei Zhang Ko et al 2017). Nevertheless, it is difficult to combine separate SWGs compactly.…”