3-bit switchable terahertz coding metasurface based on Dirac semimetals

The 3-bit coding metasurface exhibits a richer coding sequence, and performs a higher degree of freedom and flexibility in manipulating Terahertz (THz) waves. In this study, we focus on a switchable 3-bit coding metasurface based on Dirac semimetals (DSMs), and its unit cell is composed of a DSM microstructure layer, a dielectric layer, and a gold bottom layer. When the Fermi level (EF) value of the DSMs layer is 100 meV, the eight basic unit cells of the 3-bit coding metasurface are constructed by varying the length of them The proposed coding metasurface realized different functions including anomalous reflections, beam splitting, generation of vortex beams with different topological charges, and radar cross section (RCS) reduction. In addition, more than −10 dB RCS reduction can be achieved in the 1.0–1.2 THz broadband range. However, as the EF value of the DSMs changed from 100 meV to 5 meV, the phase difference of the eight cells decreases sharply, and the phase gradient of the coding metasurface gradually decreases. We designed four coding metasurfaces that implement four different functions respectively. At the same time, by changing the Fermi level of Dirac, the switching functions of four functions are respectively realized.