Design and analysis of terahertz multifunctional tunable metasurfaces based on single-layer square split ring

Aiming at the problems of single function, limited application range and complex structure of most metasurfaces, we propose a terahertz multifunctional tunable metasurface based on VO2-metal hybrid structure. The metasurface consists of three layers, from top to bottom, VO2-metal resonance layer, Topas dielectric layer and bottom gold film reflective layer. When circularly polarized light is incident, the metasurface can achieve broadband circular dichroism (CD) function, and the CD intensity generated at 3.19–6.24 THz is greater than 0.8, and the relative bandwidth is as high as 64.69%. When linearly polarized light is incident, the dual-band reversible linear dichroism (LD) function, broadband linear-to-circular polarized conversion function, and high-efficiency linear cross-polarization conversion function can be achieved by adjusting the polarization state of the incident light. Moreover, by adjusting the conductivity of VO2 and the state of the incident light, the adjustment of each functional intensity can be achieved. Finally, we believe that the proposed multifunctional metasurface has significant reference value in the terahertz range for constructing chiral photodetectors, CD metamirrors, intelligent switches, and polarization digital imaging systems.