Multiband ultrathin chiral metasurface for polarization conversion, symmetric and asymmetric transmission

This paper presents a planar chiral metasurface with two layers of omega-shaped unit cells placed on opposite sides of a substrate. The metasurface achieves linear-to-circular polarization conversion within a single band and cross-polarized transmission of linearly polarized incident waves in five bands. Due to the asymmetry and anisotropy of the metasurface in its plane, the linear-to-circular and cross-polarization conversion transmission bands are asymmetric in nature. The structure also exhibits a symmetric co-polarized transmission band for both x- and y-directed incident E-field orientations. The proposed structure gives good response for incident angles up to 600 from 3 GHz to 11.5 GHz and up to 300 from 11.5 GHz to 13.5 GHz for both transverse-electric and transverse-magnetic incidence. It is also ultrathin and has a thickness of λ0/64.7, where λ0 is the free space wavelength at the lowest frequency of operation. The proposed MS can be used for S, C, X as well as Ku microwave band applications.