Multi-band asymmetric transmissions based on bi-layer windmill-shaped metamaterial* *Project supported by the National Youth Foundation of China (Grant Nos. 11904200 and 11704219), the National Natural Science Foundation of China (Grant No. 11774053), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20190726), the Natural Science Foundationof the Jiangsu Higher Education Institutions of China (Grant No. 18KJD140004), NJUPT-SF (Grant No.

Abstract

This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90° and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions (ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effect scan be flexibly modulated in a broad multi-band from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.