Vanadium Dioxide-Based Bifunctional Metamaterial for Terahertz Waves

A vanadium dioxide-based multilayer metamaterial is proposed with bifunctional properties of absorption and polarization conversion. When vanadium dioxide is in the metallic state, the designed system behaves as a single-band absorber which is composed of a vanadium dioxide disk-shaped array, a silica spacer, and a vanadium dioxide continuous film. The performance of absorption can be tuned by changing either the diameter of disk or the thickness of silica. The design of this absorber is robust against incident polarization and incident angle. The proposed single-band absorber may be generally applied for plasmonic detection, cavity resonator, and optical band-stop filter. When vanadium dioxide is in the insulating state, the designed system behaves as a cross polarization converter which mainly consists of a one-dimensional metallic strip-shaped array, a silica spacer, and a metallic continuous film. The designed metamaterial can convert a linear plane wave into its corresponding cross-polarized wave with the efficiency of >90% in the frequency of 2.0-3.0 THz. The physical mechanism of polarization conversion is explained by a simple picture. The proposed metamaterial could be a potential candidate for the modern device of polarization control.