Asymmetric transmission and polarization conversion of linearly polarized waves with bilayer L-shaped metasurfaces

We numerically and theoretically investigate the optical anisotropy of ultra-thin bilayer L-shaped metal metasurfaces separated by a 200-nm-thick silicon dioxide (SiO2) substrate spacer. A broadband asymmetric transmission (AT) to forward and backward propagate electromagnetic waves can be acquired from linearly polarized waves. Additionally, narrowband cross-polarization conversion (CPC) can be realized by x linearly polarized electromagnetic illumination. The calculated results demonstrate that the full width at half maximum (FWHM) of AT is 965 nm, and the maximum value of the asymmetric parameter can reach up to 0.48. The polarization conversion rate (PCR) for CPC is more than 80%.