Ultra-narrow band absorber capable of being tuned from visible light to intermediate infrared light

The invention discloses an ultra-narrow band absorber capable of being tuned from visible light to intermediate infrared light. The ultra-narrow band absorber structurally comprises a substrate, a bottom Bragg reflection layer, a resonant cavity layer, a lower electrode, a dielectric spacer layer, an upper electrode, a graphene double-layer structure capable of being subjected to mutual electrostatic grid control and a top Bragg reflection layer. The absorber is based on Fabry-Perot cavity resonance, and a resonance mode is formed in a resonant cavity layer between a bottom Bragg reflection layer and a top Bragg reflection layer. The radiation loss rate of the resonance mode is mainly determined by the composition components and the period number of the Bragg reflection layer and the Fermi level of the graphene, and the absorption loss rate is determined by the Fermi level of the graphene. The bandwidth of the resonance mode is jointly determined by the radiation loss rate and the absorption loss rate. The Fe