A VO2 film-based multifunctional metasurface in the terahertz band

We proposed a multifunctional terahertz metasurface based on a double L-shaped pattern and a vanadium dioxide (${\mathrm{VO}}_2$) film separated by polyimide. When the ${\mathrm{VO}}_2$ film is an insulator, a dual-band electromagnetically induced transparency effect is obtained, and the physical mechanism is investigated based on the current distribution and “two-particle” model. When the ${\mathrm{VO}}_2$ film is a metal, a dual-band linear-to-circular polarization converter, in which the $y$-polarized linear wave can be effectively converted to left-handed circularly polarized (LCP) and right-handed circularly polarized simultaneously in different bands, can be achieved. By arranging the metal pattern rotating 30°, a multifunctional antenna can be obtained. When the ${\mathrm{VO}}_2$ is an insulator, the radiation of the LCP wave is divided into four beams, with two beams reflected and two beams transmitted. When the ${\mathrm{VO}}_2$ is in the metallic state, we can only get the co-polarized reflected wave with a 21° angle. Moreover, in our design, the ${\mathrm{VO}}_2$ film does not need lithography to obtain certain patterns, which improves the convenience of fabrication and experiment. Our design opens a new way for the development of multifunctional terahertz devices and has potential applications in the terahertz communication field.