Efficient asymmetric transmission for wide incidence angles using bi-layered chiral metasurface

An ultrathin bi-layered chiral metasurface manifesting asymmetric transmission for linear polarization is designed and experimentally demonstrated. By breaking certain symmetries of the chiral structure, the proposed design is enabled to convert a y-polarized wave into an x-polarized upon transmission in the forward direction with transmission coefficient 0.95 while an x-polarized wave is completely reflected. On the other hand, in the backward direction, an x-polarized wave is transformed into y-polarized with transmission coefficient magnitude of 0.95 while a y-polarized wave is reflected. More importantly, the proposed structure maintains asymmetric transmission characteristics for oblique incidence up to 60° both for transverse electric and transverse magnetic polarizations. It is shown that unlike linear polarization, the proposed metasurface shows no propagation direction-dependent characteristics for circular polarization. The ultrathin thickness (0.026λ at 10 GHz), efficiency and high angular stability qualifies the proposed metasurface to be a promising candidate for integration with numerous microwave devices.