Switchable Bifunctional Metasurface for Broadband Polarization Conversion and Perfect Absorption in Mid-Infrared Band

Traditional metasurfaces cannot adjust electromagnetic modulation functions once the structure is determined. Vanadium dioxide (VO 2 ) can transition from an insulating state to a metallic state at different temperatures. In this paper, we have designed a bifunctional metasurface based on VO 2 for application in the mid infrared band. The metasurface is composed of silver nanobricks and VO 2 rings, achieving broadband polarization conversion and perfect absorption through the insulator metal phase transition of VO 2. When $\mathrm{T}=303\mathrm{K}$ , VO 2 is in an insulated state, and the designed metasurface serves as a polarization converter. In the wavelength range of 3100nm to 4030nm, the polarization conversion rate exceeds 99%. When $\mathrm{T}=373\mathrm{K}$ , VO 2 is in a metallic state, and the designed metasurface serves as an absorber with an absorption rate of over 90% in the range of 4600nm to 5050 nm. At a wavelength of 4850nm, the absorption rate is 93%. The designed bifunctional metasurface can provide a new approach for the development of switchable functional components in phase change materials.