Switchable quadruple narrowband to broadband terahertz perfect absorber based on graphene and VO2 metamaterials

The article describes a switchable and adjustable terahertz perfect absorber to achieve quadruple narrowband absorption and broadband perfect absorption, consisting of graphene and VO2. Two operating modes can be toggled on account of the electrical tunability of graphene and the reversible insulating property-metallic property transformation of VO2. If VO2 displays as the insulating property, our proposed terahertz absorber manifests as quadruple narrowband perfect absorption mode. Four absorption formants can be altered effectively via adjusting the graphene Fermi energy. And then VO2 is adjusted to the metallic property, the proposed terahertz absorber possesses over 99 % absorption in 6.71–9.75 THz as broadband perfect absorption mode. A variation in the conductance of VO2 can regulate broadband absorption efficiency from 0 % to nearly 100 %. And under this condition, if the conductance of VO2 maintains in 200 S/m, it is possible to utilize broadband perfect absorber as a total reflector. Moreover, the absorption performances of both quadruple narrowband perfect absorption mode and broadband perfect absorption mode are rather polarisation-insensitive and wide-incident-angle tolerant. Generally speaking, the proposed meta-device possesses a better absorption performance, accomplishing the switch of different absorption modes and dynamic regulation of absorption performances under different modes, which can satisfy the function needs under different situations. It is believed that our design can facilitate the development of potential applications of terahertz technology in the field of filters, optical switches and sensors.