Terahertz polarization modulator based on chiral metasurface integrated with vanadium dioxide

Conventional optical polarization modulation depends on block birefringent devices, and currently there are still no commercial polarization modulation devices available for terahertz beams in free space. Metasurfaces present more opportunities for the manipulation of optical and terahertz waves, which are advantageous for highly efficient polarization modulation devices. In this paper, what we believe to be a new chiral metasurface for the polarization modulation of reflected terahertz waves is proposed that consists of vanadium dioxide (VO 2 ) combined with metal patterns for active chiral meta-atoms. Through electric stimulation, dynamic modulation of the polarization state can be achieved. The results indicate that the metasurface shows a strong circular dichroism at an operating frequency of 0.192 THz. In the insulating state, the absorption of the right-circularly polarized (RCP) wave is significantly higher than that of the left-circularly polarized (LCP) wave. By adjusting the transition state of VO 2 , the chirality of the structure is reduced, enabling the reflected wave to be switched from a circularly polarized state to a linearly polarized one. The absorption and polarization of terahertz wave can also be controlled by the incident angle. This method is anticipated to promote the development of terahertz communication and imaging technologies.