Terahertz multifunctional metasurface with broadband absorption and polarization conversion based on vanadium dioxide

Based on the metal insulation phase transition performance of vanadium dioxide (VO 2 ), we design a dual-function terahertz metasurface device that can switch between broadband absorption and polarization conversion capabilities. When VO 2 is in a metallic state, the device is a broadband absorber with an absorption rate of over 90% with an extremely wide bandwidth from 1.28 THz to 3.07 THz, and its performance stability remains highly robust to changes in incident angle and polarization. When VO 2 is in an insulating state, the device behaves as a polarization converter and functions as a dual-channel polarization converter. It can convert linear polarization to circular polarization. The efficiency of linear to cross polarization conversion is above 90% between 1.46 THz and 2.28 THz. The ellipticity of linear to circular polarization is higher than 0.9 at 0.75-1.69 THz, 2.48-2.59 THz, and 2.81-2.90 THz. The designed multifunctional metasurface has the advantages of broadband and multifunctionality, concentrating multiple functions on a single device, and has great potential in terahertz device applications.