Tunable dual-band dual-polarization terahertz polarization converter and coding metasurfaces based on Weyl semimetals

In this work, the tunable dual-band split ring terahertz (THz) polarization converter is proposed based on Weyl semimetals (WSMs). By changing the chemical potential of the WSMs, the polarization converter can realize the frequency-dependent linear-linear and circular-circular cross-polarization conversion in the two bands of 1.21-1.29 THz and 1.97-2.04 THz, respectively. The achieved polarization converter ratio (PCR) is higher than 99% for the two types of cross polarizations. Besides, the WSM-based polarization conversion also shows 2 pi phase shift and amplitude modulation by rotating the azimuth angles of the split ring. Furthermore, the 3-bit coding metasurfaces can achieve tunable linear-linear, circular-circular, and linear-circular beam modulation by adjusting the chemical potential of the WSMs. The proposed tunable metasurface would have wide applications in multiband cross-polarizations and different types of wave modulation with linear-linear, circular-circular, and linear-circular.