Switchable coding metasurface for flexible manipulation of terahertz wave based on Dirac semimetal

In this study, a switchable coding metasurface was demonstrated in the terahertz (THz) frequency range to realize dynamic beam steering based on a Dirac semimXetal. The relative phase delay of the proposed metamaterials unit cell can be actively controlled by changing the Fermi level (EF) of the Dirac semimetal film (DSF). For the 1-bit coding metasurface, the coding units with '0 ' and '1 ' states can be switched on/off in the frequency range of 1.46-2 THz by changing the EF value of the DSF. The beam numbers and propagation direction of the reflected waves in such 1-bit coding metasurfaces can be engineered at will. Moreover, a dynamically controlled 2-bit coding metasurface was constructed based on DSF microstructures to realize more sophisticated beam manipulation. When EF was set to 0.3 eV, the relative phase delay of the four-unit structure at 1.0 THz was increased from 0 degrees to 360 degrees with an interval of 90 degrees. When EF decreased to 0.02 eV, the relative phase delay of the four-unit structure was reduced accordingly, and the phase coverage decreased to only 30 degrees. Based on the above results, switching between abnormal/specular reflection and on/off vortex generation were realized. The proposed coding metasurfaces are promising for use in THz communication and sensing applications.