Multifunctional metasurface for broadband absorption and polarization conversion based on graphene-VO2

A multifunctional metasurface based on graphene and vanadium dioxide (VO2), which can function as a broadband absorber, half-wave plate (HWP), and quarter-wave plate (QWP) in the terahertz frequency band, is designed in this study. When VO2 is in the metal phase, the multifunctional metasurface operated as a broadband absorber in the range of 0.89–2.36 THz. The designed multifunctional metasurface can switch between HWP and QWP by adjusting the Fermi energy of graphene through voltage biasing when VO2 is in the insulated phase. When the Fermi level of graphene is 0 eV, the designed structure acts as an HWP to achieve linear-to-linear (LTL) polarization conversion and preserve the reflection chirality of circular polarization at 0.68–2.64 THz. When Ef = 0.3 eV, the designed structure functions as a QWP in 0.89–2.51 THz to realize the interconversion of linear polarization and circular polarization. Furthermore, the effects of the polarization and incidence angles on the operating performance are discussed. This study demonstrates that the multifunctional metasurface has promising applications in terahertz optical switches, electromagnetic stealth, modulators, and communication systems.