Two bits dual-band switchable terahertz absorber enabled by composite graphene and vanadium dioxide metamaterials

This article presents the design of a 2-bit dual-band switchable terahertz absorber using a stacked combination of graphene and vanadium dioxide (VO₂) metamaterials. For the first time, the proposed absorber design offers four switchable states by controlling the conductivity of graphene and VO₂ metamaterial layers. The lower absorption band is produced by the graphene metamaterial, whereas the upper band is implemented by the VO₂ metamaterial pattern. The structure shows two absorption bands (State 11) at 0.745-0.775 THz and 2.3-5.63 THz, when the Fermi graphene level of graphene is 0.2 eV and the VO₂ is in the metallic phase. The lower absorption band is turned off, while keeping the upper band (State 01), when the graphene Fermi level is 0 eV and the VO₂ layer is in the metallic phase. The upper absorption band is turned off, while preserving the lower absorption band (State 10) by switching the VO₂ into the insulator phase and keeping the graphene Fermi level at 0.2 eV. Finally, both of the absorption bands are turned off by setting the graphene Fermi level to 0 eV and switching the VO₂ into the insulating phase. Equivalent circuit modelling analysis and full-wave electromagnetic simulations are used to explain the operation principle of the proposed absorber. Very good agreement is obtained between the theoretical analysis and the simulations confirming the presented design principle for the 2-bit switchable absorber.