Switchable dual-broadband to single-broadband terahertz absorber based on hybrid graphene and vanadium dioxide metamaterials

Abstract

Switchable and tunable broadband perfect absorbers have drawn great interest in a wide range of applications, including modulation, energy harvesting, and spectroscopy. Here, we propose a switchable and tunable terahertz (THz) metamaterial absorber with dual-broadband, single-broadband perfect absorption using graphene and vanadium dioxide (VO2). Simulation results show that, when VO2 is in the insulated state, this design behaves as a dual-broadband absorber with over 90% absorption in 0.73 THz–1.53 THz and 3.03 THz–3.64 THz under normal incidence. When VO2 is in the metallic state and the graphene Fermi energy is set as 0.01 eV, this design acts as a single-broadband absorber with over 90% absorption in 1.00 THz–3.55 THz and the fractional bandwidth reaches 112%, which is much larger than the previously reported values. The absorption rate can be dynamically tuned by individually changing the conductivity of VO2 and the Fermi energy of graphene. Moreover, this design exhibits polarization-insensitive and wide-incident-angle behaviors for both TE and TM waves. Such a design may have potential applications in many fields, such as thermal detectors, modulators, and stealth technology.