Adjustable terahertz circular dichroism and sensing characteristics of chiral metasurfaces

We propose a circular dichroism metasurface that achieves absorption, reflection, and sensing functions for terahertz waves. It consists of an inverted U-shaped resonator, Topas dielectric, and a metal substrate. This structure exhibits dual-band circular dichroism in the frequency range of 2.0–5.0 THz, with an absorption rate of 95.46% and a circular dichroism value of 0.90 for left circularly polarized waves at 3.20 THz. The absorption rate of right circularly polarized waves at frequency of 4.12 THz is 99.63%, and the circular dichroism value is 0.99. By changing the conductivity of vanadium dioxide and photosensitive silicon in the U-shaped resonator, depth modulation of 97.78% and 86.87% can be achieved, respectively. The sensitivity of two resonant peaks to analytes with refractive indices ranging from 1.1 to 1.4 reached 1850 and 2300 GHz/RIU, respectively. This terahertz chiral metasurface has potential applications in polarization detection, chiral sensing, biomedical, and other fields.