Design And Study Of Graphene-based Tunable Metamaterial Absorber

Metamaterials are a new type of composite material,with remarkable characteristics such as negative magnetic permeability(μ),negative dielectric constant(ε),inverse doppler effect,inverse wave transmission and perfect absorption,have been focused by many researchers in recent years due to their remarkable optical properties.In this paper,we investigate the absorber properties of metamaterial absorbers based on graphene material instead of the traditional noble metals.CST Microwave Studio 2019(CST),an electromagnetic simulation software,is used to analyze and study the tunable,polarizationinsensitive/sensitive,high-performance absorption and large-angle incidence of the proposed metamaterial absorbers.Utilizing impedance matching theory and multiple reflection interference theory,the simulation results are compared and verified,and the practical applications are further discussed.The detailed research contents that have been carried out in this paper are as follows.(1)At first,a graphene-based single-band metamaterial perfect absorber is designed,which is a classical "sandwich" structure with a gold layer of sufficient thickness as the bottom ground,a TOPAS layer with dielectric constant of 2.35 acting as the middle layer,and a graphene pattern layer being set on the top.The absorption peak with peak absorbance near 100% is found at the frequency of 5.485 THz for TE or TM polarized incident electromagnetic waves.Verification of the simulation results is conducted through the utilization of multiple reflection interference theory(MRIT)and impedance matching theory(IMT),and the results demonstrate that the theoretical results are well agree with the simulation results.(2)At second,a new type of graphene-based tunable metamaterial perfect absorber is designed,which is also a classical and simple sandwich structure consisting of a nonrotationally symmetric graphene pattern layer,a TOPAS dielectric layer and a sufficiently thick gold ground plane.The proposed absorbers absorption characteristics are demonstrated to be polarization-sensitive and dynamically adjustable,which can produce dual-band absorption at 4.268 THz and 6.032 THz with peak absorption coefficients as high as 99.99% and 99.79%,respectively,for TE-polarized incident electromagnetic waves.The influence of the geometrical parameters,the chemical potential and the relaxation time of graphene on the absorption of the proposed absorber are examined in detail.Verification of the simulation results is accomplished through the utilization of MRIT and IMT,and which demonstrates that the theoretical results are well agree with the simulation results.Besides,TE light can be absorbed effectively by the absorber across a broad range of incident angles.Furthermore,good terahertz switching performance can be achieved by choosing different graphene chemical potentials.Meanwhile,applications in refractive sensing are investigated in detail,where higher sensitivity and figure of merit(FOM)can be obtained.