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 2π 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.