A high-performance transmissive circular polarization converter based on a modified fishnet metasurface.

We propose a transmissive circular polarization converter with reduced thickness and high performance. The proposed device is composed of a three-layer metasurface spaced by two dielectric plates. The top and bottom layers are metasurfaces formed by meander lines, and the middle metasurface is a modified fishnet structure etched periodically with gaps along the x-direction. By employing these periodic gaps, the bandwidth of the proposed device is significantly extended. The simulation results reveal that the device can convert a linearly polarized incident wave into a circularly polarized transmissive wave in wideband from 10 to 16 GHz, with relative bandwidth of 46%. Fortunately, the device's bandwidth can still cover the range of 10–13.8 GHz even when the incident angle increases to 40°. Meanwhile, two equivalent circuit models for two orthogonal polarizations are accurately extracted to better understand the physical mechanism of bandwidth expansion. An experimental sample is fabricated to verify the device performance. The experimental results are in reasonable agreement with simulations. [ABSTRACT FROM AUTHOR]