Design of a switchable and tunable terahertz metamaterial absorber with broadband, ultra-broadband, and dual-broadband absorption based on graphene and vanadium dioxide

This work develops a switchable and tunable terahertz metamaterial absorber based on graphene and vanadium dioxide (VO₂). The nesting of graphene square rings (GSRs) and VO₂ square rings (VSRs) forms the top layer, and a VO₂ intermediate layer (VIL) sandwiched between two dielectric layers is placed on a gold mirror. The absorber can be flexibly switched among broadband absorption (BA), ultra-broadband absorption (UBA) and dual-broadband absorption (DBA) by means of voltage-controlled GSRs and temperature-controlled VSRs and VIL. The BA dominated by the metallic state of the VIL has an absorption bandwidth of 5.273 THz, while the bandwidth broadens to 7.103 THz to become UBA as VSRs transform into the metallic state. Meanwhile, when the VIL is in the insulating state, GSRs with a Fermi energy level of 1 eV and VSRs in the metallic state work together to generate DBA with bandwidths of 1.776 and 1.994 THz. Moreover, the proposed absorber not only allows flexible function switching and efficient dynamic tunability, but also has polarization insensitivity and large incident angle tolerance. Such a design may provide new ideas and methods for designing switchable multifunctional terahertz metamaterial absorbers, which have potential for application in stealth technology, modulators and detectors.