Microwave linear polarization rotator in a bilayered chiral metasurface based on strong asymmetric transmission

We propose and study a kind of bilayered chiral metasurface (BCM) composed of complementary L-shaped resonators with a lossless dielectric spacer that can realize linear polarization rotation with ultrahigh conversion efficiency. We present a theoretical analysis of the BCM with specific chiral geometry that enables asymmetric transmission for linear polarization only. Numerical results show that the proposed metasurface has dual-band asymmetric transmission with nearly 100% cross-polarization conversion efficiency when the loss is ignored. More importantly, depending on the incident direction, only one of the cross-polarization transmissions can approach unity while all the remaining transmissions are close to zero. As a result, nearly perfect linear polarization rotation is achieved for a particular polarization direction. We further show that the working frequency and the bandwidth of the proposed BCM can be tuned by adjusting the geometric size and spatial arrangement of the unit cell.