Design And Research Of Terahertz Absorber Based On Graphene And Dirac Semi-metal Metamaterials

Terahertz wave is a band between micro-wave and light-wave and has unique properties that different from micro-wave and light-wave.The special properties of terahertz wave has made the terahertz wave become a hot spot in academic research.In the process of research and application of terahertz wave,terahertz devices with excellent performance are necessary to realize the detection and modulation of terahertz wave.In order to design the terahertz devices with excellent performance,it is necessary to select suitable materials that has well respond to terahertz wave.With the advent of graphene,its special electromagnetic properties have a good response to terahertz waves,and the Fermi level of graphene can be adjusted by applying a voltage to it,so that the devices can modulate the terahertz waves.On the basis of graphene researching,the academic community has developed Dirac semi-metal metamaterial which has similar properties to graphene but with a three-dimensional structure.It also shows great application prospects in the terahertz absorbers design.This article mainly introduces the design of terahertz absorbers based on graphene and Dirac semi-metal metamaterials.The main contents are as follows:(1)Graphene and Dirac semi-metal metamaterials have unique electromagnetic properties,and the complex permittivity of them can be described through Kubo’s formula.At the same time,a method of applying a voltage to graphene to change the Fermi level of graphene in order to adjust its complex permittivity is given,so that the terahertz wave can be realized.Electromagnetically induced transparency theory(EIT),interference absorbing principle and impedance matching theory are also basic theories for the design of terahertz absorbing devices,and important parameters and indicators used to evaluate the absorbing performance of absorber are also given.(2)A kind of terahertz absorber based on graphene notch ring was designed,and the influence of related structural parameters on the performance of the device was investigated through simulation,and the optimal structural parameters were optimized,so that the absorption rate of designed terahertz absorbers can reach more over 95%,and the absorber also has good tunability.On this basis,through the concentric nesting of graphene notch rings,terahertz absorbers with two or even three absorption peaks have been realized,and the absorption rate of every absorbers designed in this paper has reached more than 90%.A method for realizing an absorber with any number of absorption peaks through the concentric nesting of graphene notch rings is proposed.(3)Based on the Dirac semi-metal metamaterial,a sandwich-structure terahertz absorber is designed,with the square ring shaped Dirac semi-metal metamaterial as the resonant unit,which has two tunable absorption peaks in the range of 5.5 THz～10 THz.In the meantime,the optimal structural parameters are optimized and obtained through simulation,and the absorber designed under the optimal structural parameters has the absorption rate more over 90% at both absorption windows.,and with the increase of the Fermi level of the Dirac semi-metal resonator unit,the absorption window will blue shift.