Temperature tunable broadband filter based on hybridized vanadium dioxide (VO₂) metasurface

Abstract In this paper, a novel temperature tunable terahertz (THz) broadband filter based on hybridized vanadium dioxide (VO 2 ) metasurface (MS) was proposed. The designed MS is composed of subwavelength metallic square-grid structure situated between two layers of metallic square-patch structure integrated with VO 2 film pad spaced with two layers of dielectric substrate. Utilizing the insulator-metal phase transition characterizations of VO 2 in the THz regime, the operation mode of the proposed MS filter accomplishes the broadband transmission-to-reflection transition. Simulation results show that when VO 2 is in the insulating state with a lower external temperature, the proposed MS behaves like a broadband filter with transparent window and a transmittance of above 80% over the frequency range of 0.66–1.12 THz. However, when VO 2 undergoes the metallic state with a higher external temperature, the MS becomes a broadband filter with low-transmission shielding and exhibiting a transmittance of below 10% across the frequency spectrum from 0.56 THz to 1.4 THz. The physical mechanism of the proposed MS based tunable broadband filter is illustrated by introducing impedance matching theory, equivalent circuit model and field analysis. In addition, the proposed MS structure offers exceptional angular stability and polarization insensitivity, opening up new opportunities for the utilization of energy selective surface in THz applications.