Broadband absorption and polarization conversion switchable terahertz metamaterial device based on vanadium dioxide

A broadband absorption and polarization conversion switchable terahertz metamaterial device can be obtained by introducing vanadium dioxide with the metal to insulate phase transition. As the vanadium dioxide is in the metallic state, the device is a broadband absorber with over 90% absorption from 1.03 THz to 2.62 THz, and the broadband absorption performance is not sensitive to both the oblique incident angle and polarization. When vanadium dioxide is in insulate state, the device performs as a polarization converter with two functions of linear to cross polarization and linear to circular polarization conversion. The polarization conversion efficiency of linear to cross polarization conversion is above 90% from 1.81 THz to 2.39 THz, while the ellipticity of linear to circular polarization conversion is over 0.9 in the ranges of 0.75–1.69 THz, 2.48–2.59 THz and 2.81–2.90 THz, respectively. The proposed bifunctional device provides the potential in THz devices with tunable and diverse functionalities.