Tunable multiband metamaterial coherent perfect absorber based on graphene and vanadium dioxide

In this paper, we propose a tunable multiband metamaterial coherent perfect absorber, where vanadium dioxide (VO2) square particles are periodically arranged on the two sides of polysilicon-silica-graphene-silica- polysilicon structure. The absorption spectrum of our absorber exhibits three peaks with high absorptivity which are originated from the plasmon resonance modes of graphene and VO2 particle. Benefitting from the tunable conductivity of graphene, the adjustment range of the absorption peak based on the first-order plasmon resonance mode of graphene is as much as 7.88 mu m when the Fermi level of graphene is increased from 0.3 to 1 eV. As VO2 is changed from metal phase to insulating phase, the absorption peak stemming from the plasmon resonance mode of VO(2 )particle disappears. The modulation depth of absorption peak can achieve up to 98.85% by tuning the relative phase of two coherent light beams. The resonance wavelengths and intensities of absorption peaks are also dependent on the array period, side length of VO2 particle and the thickness of silica layer. In addition, the change of surrounding refractive index causes a shift of the absorption peak corresponding to VO2 particle. Our findings are helpful for the engineering of actively tunable nano plasmonic devices and metamaterials.