Ultra-broadband and wide-angle terahertz polarization converter based on symmetrical anchor-shaped metamaterial

We propose a reflective terahertz metamaterial linear polarization converter, consisting of three layers: an array of metallic symmetrical anchor-shaped resonators, poly tetra fluoroethylene (PTFE) as a low loss dielectric layer, and a metal surface ground plane. The simulation results show that the proposed metamaterial can convert the linearly polarized waves into the cross-polarized waves with a polarization conversion ratio (PCR) of above 93% in the frequency range of 1.21-2.83 THz and the relative bandwidth is as high as 80.2%. The proposed metamaterial is valid for a wide range of incident angles, and the average polarization conversion ratio remains 93% even though the incident angle reaches 45 degrees. Additionally, we theoretically analyzed the conversion mechanism of achieving a high-efficiency linear polarization conversion in a wide frequency range by calculating the polarization angle and elliptical angle of the reflected terahertz waves. The experiment results using the terahertz time domain spectroscopy (THz-TDS) consist well with the simulation results. Our design will provide an important reference for the practical applications of the metamaterials in polarization manipulation.