Dynamically switchable tri-functional THz-integrated metamaterial absorber based on VO2-graphene

Based on the easily accessible phase transition temperature of VO2 and the electrically tunable properties of graphene, a tri-functional THz-integrated metamaterial absorber with dynamically switchable low-frequency broadband, high-frequency broadband, and multi-band absorption are proposed. This absorber is composed of a patterned VO2 layer, a SiO2 dielectric layer with a layer embedded patterned graphene, a thick unpatterned VO2 layer, both sides of which are coated with ML graphene, a SiO2 dielectric layer, and an Au substrate. When the patterned and unpatterned VO2 layers are both metallic, the proposed absorber behaves as a low-frequency broadband absorber from 2.7 to 6.2 THz with average absorptivity exceeding 90 %, with the value of absorption sensitive to the structure of the patterned VO2. When the patterned VO2 is insulating and the unpatterned VO2 is metallic, the absorber exhibits high-frequency broadband absorptivity, above 90 % from 5.8 to 7.6 THz. When the patterned and unpatterned VO2 are both insulating, the device acts as a multi-band absorber with 12 tunable resonance peaks. In addition, the proposed absorber is robust against the incidence angle and polarization. Furthermore, the electric field strength distributions and multiple interference theory are presented to explain the physical mechanisms of tri-functional near-100 % absorptivity. Our work may provide a promising path for the development of multifunctional THz-integrated metamaterial absorbers.