Thermally tunable wideband and bifunctional plasmonic-VO2 metasurface in THz region

Abstract

In this paper, a thermally tunable plasmonic-VO2 metasurface with wideband bifunctionality is introduced and studied. This planar structure can be a wideband polarization converter and absorber based on insulator to metal phase change of VO2. In room temperature, the introduced metasurface is a linear (LP) to circular (CP) polarization converter for which the ellipticity is more than 95% and its operating bandwidth is 36.55 % in the wavelength range of 1.91 to 2.77 (μm). By increasing temperature up to 358 (K), VO2 faces phase change to metallic state and then the proposed metasurface acts as an absorber of electromagnetic waves for which the absorbance is more than 80% and its operating bandwidth is ~ 71%, in the wavelength range of 1.68 to 3.5 (μm). For this bifunctional metasurface, its ellipticity for the converter and absorbance for the absorber is almost insensitive to incident angle (θ°) up to 25° and 30° respectively for the both TE and TM modes. The effects of the polarization angle (φ°) is also studied and shown that by increasing polarization angle up to 90° in the absorber case, the working bandwidth of absorber is unaltered.