Bidirectional chiral terahertz metasurface with circular dichroism and asymmetric transmission

We propose a bidirectional terahertz chiral metasurface with multifunctions of circular dichroism (CD) and asymmetric transmission (AT). When vanadium dioxide (VO 2 ) is in a metallic state, the metasurface exhibits tri-frequency circular dichroism when circularly polarized waves are incident along the − z direction. As circularly polarized waves are incident along the + z direction, the circular dichroism value of the metasurface is more than 0.8 within the frequency range of 6.60–7.24 THz. When both vanadium dioxide and photosensitive silicon are in a dielectric state, the metasurface exhibits a linear asymmetric transmission effect, with a maximum AT of 0.80. At the same time, the metasurface produces linear polarization conversion with a polarization conversion rate (PCR) of more than 0.9 within the frequency range of 3.22–4.99 THz. The proposed bidirectional terahertz chiral metasurface offers an approach that effectively manipulates electromagnetic waves and exhibits potential application prospects within the domains of polarization detection, satellite communication, imaging display, and radar.