Active manipulation of Dirac semimetals supported chiral coding metasurfaces for multifunctional applications in terahertz region

Multifunctional coding metasurfaces can provide more options for highly integrated terahertz modulators, which has become one of the current research focus. This study proposed a tunable chiral metasurface based on a Dirac semimetal (DSM). Two U-shaped rings placed perpendicular to each other in the opening direction comprised the metasurface unit cell. Further, the multifunctional application of the metasurface in the terahertz region was realized through coding. The chiral metasurface exhibited strong chirality for incident circularly polarized light with circular dichroism (CD) of up to 0.72 at 2.31 THz. The combination of the chiral metasurface with the Pancharatnam-Berry (PB) phase aided in the realization of a wideband switchable terahertz vortex beam generator, arbitrary angular deflection tuning of the vortex beam, and multi-beam splitting operation of the vortex light using a Fourier convolution operation. In addition, switchable near-field imaging applications were developed by encoding metasurface unit cell cells according to their chirality and amplitude. The results of this study are expected to yield promising applications in future terahertz high-data-capacity communication systems, multi-target information transmission, and controlled near-field imaging.