Research On Graphene-based Multi-band Tunable Metamaterial Absorber

Metamaterials are compound materials composed of artificially designed geometrical structure,which has unique and excellent electromagnetic properties that cannt be found in natural materials.Metamaterial absorber is one of the important branch in the common research fields of metamaterial.In this paper,graphene,a type of novel 2D material,is applied to replace the noble metal in the designe of metamaterial absorbers.Numerical simulations are carried out using the electromagnetic simulation software CST MWS,which will be operated in frequency domain.Meanwhile,comparative studies of the absorption properties are also applied through the combination of the impedance matching theory and multi-reflection interference theory.In terms of the unique properties of graphene material and the real application demand of metamaterial absorber in THz frequency range,the following research contents will be done in this thesis.(1)A dual-band tunable perfect absorber based on “(?)” type graphene pattern arrays is designed.The influence of geometric parameters,material parameters,and incidence angle of the electromagnetic wave on the absorption characteristics are studied.At the same time,combining with the distribution of electric field and surface current,the physical mechanism of the formation of the perfect 2-band absorption is analyzed.The results are verified and analyzed through multi-reflection interference theory and impedance matching theory.In addition,the application of the structure in the field of refractive sensing is studied by covering the surface of the structure with dielectric materials with different refractive indexes.Simulation results show that the structure has high sensitivity()and figure of merit().This kind of metamaterial absorber structure has potential applications in electromagnetic cloaking,filtering,biochemical sensing and detection.(2)A four-band tunable metamaterial absorber composed of periodically agrranged graphene pattern arrays is designed,which is composed of graphene split rings and L-shaped graphene cross pattern.The simulation results show that the designed absorber structure supports four perfect absorption bands in the range of 3-11 THz.Meanwhile,the absorption bands can be dynamically adjusted by changing the structural parameters and the graphene Fermi level.At the same time,the proposed absorber structure has the characteristics of polarization insensitivity,and has a good tolerance to the incident angle of the input electromagnetic wave.Furthermore,the sensing applications under two different ways are studied,and the results show that the absorber structure has high sensitivity()and figure of merit()in both two sensing approches.The absorber has broad application prospects in the fields of electromagnetic cloaking,THz filtering,optical senssing and integrated photodetections.