A perfect absorber of multi-band, tunable monolayer patterned graphene based on surface plasmon resonance

Abstract

A triple-band ultra-perfect absorber with tunability based on graphene surface plasmon resonance is investigated and proposed in this article. According to the finite difference time domain (FDTD) method, in the mid-infrared wavelength range of 3400 nm ∼ 4000 nm, we have identified three perfect absorption peaks, namely at λ1 = 3548.54 nm, λ2 = 3660.25 nm and λ3 = 3912.99 nm, in which the absorption rate 99.90 %, 99.05 %, 99.13 % respectively. By discussing different graphene geometries, this paper shows the best results of this experiment. If we want to control the amplitude of the absorption peak and the wavelength of the resonance, we can do so in two ways: first, by changing the Fermi energy level of the graphene, and second, by changing the relaxation time of the graphene. Besides, the absorbed resonant waves can slao be controlled by adjusting the refractive index of the environment in which they are located and the refractive index of SiO2. The absorber exhibits polarisation and angle insensitivity, so when the angle of incidence varies in the (0° ∼ 50°) range, the absorber we have designed also maintains high absorption. Three resonance absorption peaks with sensitivities of 845.7 nm/RIU, 880.3 nm/RIU and 942.6 nm/RIU can be obtained from the results of the simulations. In summary, we believe that the absorber with its various characteristics could be of great value in a number of applications.