Research On Tunable Terahertz Absorber Based On Graphene Surface Plasmon

Terahertz wave(THz)is an electromagnetic wave with a frequency between 0.1and 10 THz and a wavelength between 30 μm and 3,000 μm.They have properties such as broadband,low energy,penetration,and high resolution,and they have promising applications for biomedical sciences,electromagnetic stealth,terahertz imaging,and high data communications.Metamaterials are new synthetic composites that do not exist in nature.The metamaterial-based absorber is an integral part of its research area.Two kinds of tunable terahertz absorbers based on graphene metamaterials have been proposed and simulated numerically using COMSOL Multiphysics,combining the theory of multiple reflection interference(MRIT)and the impedance matching theory.Several aspects of the proposed terahertz absorber are investigated,primarily as follows.(1)A tunable dual-band terahertz absorber with a "broken wheel" graphene pattern is proposed.The effects of graphene chemical potential,relaxation time,geometric structure,angle of incidence and polarization angle on absorption performance are investigated.At the same time,the forming mechanism of the absorption band is analyzed by the electric field distribution on the graphene super surface,and the simulation results are theoretically validated by combining the impedance matching theory and multiple reflection interference theory.In addition,by changing the refractive index of free space,the application of a metamaterial absorber in a refractive index sensor is discussed.(2)A tunable three-band terahertz absorber with a two-layer graphene array is proposed based on a single-layer graphene absorber.The simulation results show that,under the given parameters,three absorption peaks are obtained at the frequencies of1.45 THz,2.18 THz,and 3.77 THz,respectively,with an absorption rate of more than96%.At the same time,the mechanism of the three absorption peaks is explained by an electric field diagram,and the simulation results are verified theoretically.The two-layer graphene absorber can independently regulate the absorption performance by individually changing the relevant parameters of one of the graphene layers.It has flexible modulation performance and wide-angle incident and polarization insensitivity properties.Based on the absorber’s good multi-band absorption function,it has bright application prospects in the fields of high-quality refractive index detection,electromagnetic stealth and optical sensing.