A multifunctional reconfigurable terahertz chiral metasurface based on VO₂ and graphene

Despite advancements in high integration and miniaturization, terahertz (THz) devices still face challenges such as limited functionality, tunability, and narrow application ranges. To resolve the above concerns, we present a multifunctional reconfigurable THz chiral metasurface based on vanadium dioxide (VO₂) and graphene. This structure exploits VO₂'s phase transition and graphene's electrical tunability, enabling multifunctional responses. The metasurface exhibits a triple-band circular dichroism (CD) response within 1.0-3.5 THz, with peaks at 1.62 THz, 2.89 THz, and 3.19 THz, reaching values of 0.944, 0.83, and 0.88, respectively. Dynamic switching of CD peak numbers is achieved through the synergistic control of VO₂ and graphene. Under linearly polarized light incidence, the metasurface shows a single-band linear dichroism (LD) response in the 4.0-4.2 THz range, with a peak value of 0.9 at 4.093 THz. The intensity of the LD response can be reversibly tuned by adjusting the Fermi level of graphene and the incident polarization angle. Additionally, the metasurface efficiently converts polarization under both x-polarized and left-handed circularly polarized light. This multifunctional metasurface offers new opportunities for THz applications, such as CD supermirrors, intelligent switches, chiral photodetectors, and polarization digital imaging systems.