Vanadium dioxide based bifunctional metasurface for broadband absorption and cross-polarization conversion in THz range

Abstract

Achieving switchable and reconfigurable functions based on a single metasurface has become one of the research hotspots among scholars in recent years. Based on the excellent phase transition properties of vanadium dioxide (VO2), a THz bifunctional metasurface device (BMD) is designed that can realize broadband absorption and broadband cross-polarization conversion. When VO2 behaves in the metallic state, the BMD acts as a broadband metamaterial absorber (MA), and its absorbance is larger than 90 % in the range of 1.97–4.63 THz with a relative bandwidth (RB) of 80.61 %. In addition, the MA is insensitive to the polarization angle and can maintain high absorbance over a wide range of incident angles for both y- and x-polarized THz waves. When VO2 behaves in the insulated state, the BMD will act as a broadband linear polarization converter (PC). It has a polarization conversion ratio (PCR) of greater than 90 % with a RB of 92.31 % in the frequency range of 1.54–4.18 THz. The excellent absorption and polarization conversion characteristics of the proposed BMD make it possess potential values in different THz areas with sub-wavelength device scales.