Bifunctional flexible metasurface based on graphene and vanadium dioxide for polarization conversion and absorption

A bifunctional flexible metasurface with high polarization conversion ratio (PCR) and absorptivity based on graphene and vanadium dioxide (VO2) is proposed in microwave band, which consists of metallic resonator with two VO2 films in the diagonal direction, graphene resistance film layer, two polyimide (PI) dielectric layers and copper ground plate. The proposed metasurface can be switched from a polarization converter to an absorber by employing insulator-to-metal transition in VO2, and the PCR and absorptivity are dynamically manipulated by the graphene. When the conductivity of VO2 (σvo2) is 10 S/m (room temperature) and the square resistance of graphene (Rg) is 900 Ω/sq., the metasurface becomes a broadband polarization converter with the PCR exceeding 90 % in 6.97–17.62 GHz and the corresponding relative bandwidth (RB) is 86.62 %. Once the temperature is high enough and VO2 is in its fully metallic state (σvo2 = 2 × 105 S/m and Rg = 30 Ω/sq), the metasurface efficiently absorbs normally incident electromagnetic (EM) waves in 13.33–19.47 GHz with the absorptivity exceeding 90 % (RB = 37.44 %). The influence of geometric and EM parameters and incident angles on its bifunctional features are also investigated. Moreover, the proposed metasurface exhibits polarization insensitivity under dual functions. The designed bifunctional metasurface is expected to be applied in the fields of wireless communication systems, radar and sonar systems and EM stealth technology.