Narrow-broadband switchable THz absorber based on graphene and VO₂

Terahertz waves possess unique electromagnetic properties, such as penetration, high capacity, and non-destructive testing capabilities, making the study of their absorption characteristics highly significant. Building on previous narrowband and broadband research, this paper introduces an absorber capable of switching between narrowband and broadband modes. This absorber leverages the tunability of graphene and the phase transition properties of vanadium dioxide (VO₂) to achieve adjustable and switchable absorption characteristics. When VO₂ is in its insulating state, the absorption spectrum exhibits dual narrowband absorption with an absorption rate approaching 100%. As the temperature increases, VO₂ transitions to a conductive state, resulting in ultra-wideband absorption with a bandwidth of 2.24 THz. Research has shown that the broadband mode is robust with respect to relaxation time and the thickness of VO₂ (within a certain range). The broadband mode is also insensitive to the angle of incidence. The narrow-to-wideband switching absorber demonstrated in this paper offers new insights for research in related fields.