VO2-Based Switchable Metasurface With Broadband Photonic Spin Hall Effect and Absorption

Arbitrary control and dynamic tuning of circularly polarized (CP) wave are of great significance to photonic research and application. Here, a terahertz switchable metasurface is designed with bifunctional properties based on a mixed structure of graphene and vanadium dioxide (VO2). The design consists of VO2 strips, topas spacer, VO2 film, graphene patch, topas spacer, and metallic film. When VO2 is metal, this metasurface realizes photonic spin Hall effect (PSHE) for CP wave in a wide frequency hand of 0.7-1.5 THz. When VO2 is insulator, the design behaves as an absorber. It has a broadband absorption with more than 90% absorptance in the range of 0.48-1.88 THz, and there are two resonant peaks with similar to 100% absorptance at 0.92 THz and 1.74 THz. Meanwhile, absorption bandwidth and intensity can be dynamically tuned by changing Fermi energy level of graphene. Besides, broadband absorption is robust against incident angle. Our design may promote the realization of terahertz switchable and multifunctional metasurfaces.

Automated summary

This study presents a terahertz switchable metasurface with bifunctional properties: it can realize the photonic spin Hall effect for CP waves when VO2 is metallic, and behaves as an absorber when VO2 is insulator. The design exhibits different absorption peaks at different frequencies, and absorption bandwidth and intensity can be dynamically tuned by changing the Fermi energy level of graphene.