Dual-Control and Tunable Broadband Terahertz Absorber Based on Graphene-Vanadium Dioxide

This paper proposes a dual-control adjustable terahertz metamaterial broadband absorber based on a mixed material of graphene and vanadium dioxide (VO2). The absorber has the advantages of simple structure, switchable absorption/ transmission/reflection, and large modulation depth. The absorptivity control of the absorber can be achieved by changing the phase transition characteristics of VO2 and the Fermi energy level of graphene. When VO2 is in a metallic state, the absorber can achieve broadband absorption with an absorptivity greater than 90% in the frequency range of 1.07-2.59 THz, and exhibits excellent absorption performance under a wide range of incident and polarization angles for TE and TM polarizations. By changing the Fermi energy of the graphene, the in-band absorptivity can be dynamically adjusted, and the modulation depth is greater than 67.2%. When VO2 is in an insulating state, the device behaves as an adjustable transmission mode regulated by the graphene Fermi energy level, with a transmittance modulation depth greater than 40%. Furthermore, by controlling both the VO2 phase transition characteristics and the graphene Fermi energy level, the in-band absorptivity modulation depth of the absorber can be increased to more than 90%, and the maximum modulation depth is 99.7%. The absorber realizes a terahertz dual-control absorber with good tuning characteristics through two independently controllable materials, and has potential applications in the field of terahertz smart devices (such as attenuators, reflectors, and spatial modulators).