Actively switchable multiband terahertz absorption and broadband reflection based on a graphene-VO2 hybrid metasurface

Abstract

Metamaterials hold significant potential for high-performance, optically reconfigurable devices; however, the development of tunable and switchable metamaterial devices in the terahertz (THz) band remains urgently needed. In this study, a switchable THz metasurface device (STMD) is proposed and numerically investigated. The device consists of patterned graphene layers embedded within dielectric spacers and backed by a metallic ground plane, enabling dynamic control of the electromagnetic response through the phase transition of VO₂ and tuning the chemical potential of graphene. Finite-difference time-domain (FDTD) simulations show that when VO₂ is in the insulating phase, and the chemical potential of graphene is tuned via an external bias voltage, the STMD exhibits triple-band near-perfect absorption, with absorption exceeding 90% across 1.43–2.08 THz, 4.98–5.47 THz, and 8.70–9.35 THz bands, reaching a maximum of approximately 99.97%, 97.96%, and 98.35%, respectively. In contrast, when VO₂ is in the metallic phase, and the graphene chemical potential is set to 0.0 eV, the structure switches to the reflection mode, exhibiting ultra-broadband high reflection exceeding 90% from 0.1–6.58 THz. Furthermore, the proposed structure demonstrates stable performance against polarization variations and structural parameter changes. These results indicate that the STMD design provides an efficient and versatile platform for actively switchable THz absorption and reflection, with potential applications in THz modulators, adaptive absorbers, switches, and reconfigurable photonic devices.