Wideband and high-efficiency planar chiral structure design for asymmetric transmission and linear polarization conversion

Abstract

The phenomenon of asymmetric transmission (AT) means the existence of a giant difference in transmittance after the incident waves pass through the special slab in two opposite directions, which is quite useful for realizing irreversible electromagnetic waves and has attracted much attention in recent years. However, it is difficult to achieve wideband asymmetric transmission and linear polarization conversion simultaneously using the bilayer transmission-mode structure. In this work, we propose and numerically investigate a high-efficiency transmission-mode metamaterial that consists of twisted multigap rings on both sides of a dielectric slab. Benefiting from the antisymmetric design of the split ring bilayer transmitarray element, the proposed structure excites the electric and magnetic dipole resonances with mutual interference, thereby simultaneously achieving asymmetric transmission and linear polarization conversion. The proposed structure is designed, fabricated, and measured, which can realize a good agreement between the measurement results and the anticipation. Within the frequency range from 12.7 to 17 GHz, the AT parameter can be close to 0.9 and the polarization conversion ratio can be more than 93%.