Design And Performance Simulation Of Graphene-Based Metamaterial Terahertz Broadband Absorber

In recent years,the application demand of terahertz wave is increasing day by day,and the application demand of corresponding terahertz device is also increasing gradually.Among them,the terahertz absorber based on metamaterial is favored by researchers because of its unique response to terahertz waves and is enjoyed by the researchers to research.However,there are always some limitations such as low absorptivity,narrow absorption bandwidth or even unregulated.Later,researchers tried adding materials such as graphene or semiconductors to the absorbers and found that they could ameliorate these shortcomings,but only to a limited extent.With the development and application of terahertz devices,it has become a research hotspot to obtain more flexible and adjustable absorbers with longer broadband and higher absorption response.In this thesis,different methods are used to improve the absorptivity of graphene-based absorbers.Three types of broadband adjustable highperformance absorbers were simulated using CST STUDIO SUITE software.1.Composite silicon hemisphere/graphene wideband terahertz metamaterial absorberA metamaterial terahertz absorber with pyramidal structure and checkerboard graphene structure is proposed.The absorber is made up of four parts: a silicon semiellipsoid/semi-spherical composite structure,graphene,a dielectric layer and a metal backplane.The absorber can achieve frequency modulation and performance of near100% absorption.When the chemical potential of graphene is 0.2 e V and 0.9 e V,ultrawideband terahertz wave absorption of about 5.7 THz and 7 THz can be obtained,and the maximum absorptivity is close to perfect absorption(about 99.8%).In addition,the structure has excellent characteristics of 360° polarization insensitivity and incident angle insensitivity higher than 60°.The above performance has potential application prospects in terahertz wave detection,spectral imaging and stealth technology.2.Composite silicon four trustum of a pyramid /checkerboard graphene wideband terahertz metamaterial absorberA metamaterial terahertz absorber is proposed,which is composed of a silicon four trustum of a pyramid,a checkerboard graphene,a dielectric layer and a metal backplane.When the chemical potential is 0.9 e V,nearly 80% absorptivity can be obtained in the whole terahertz band.The total absorption bandwidth can reach 5.6 THz,and the highest absorptivity can reach 98.6%.Moreover,the sensitivity of 60° incident angle and 360° polarization angle is maintained.The absorption realizes the characteristics of broadband adjustable absorption and has great application potential.3.Gallium arsenide(Ga As)/ graphene composite dynamically adjustable wideband terahertz metamaterial absorberA metamaterial terahertz absorber consisting of a Ga As/cross graphene absorber and a cross graphene absorber is proposed.The absorber can be converted between Ga As metal state and insulating state by irradiating pump light.When Ga As is in metallic state,the absorption bandwidth is up to 3.3 THz and the maximum absorptivity is up to 99.51%.When Ga As is in the insulating state,the total absorption bandwidth can reach 2.4 THz and the maximum absorptivity is up to 99.99%.The total bandwidth of the two states is 4.7 THz,and both have an incident angle of more than 60° and an insensitivity of 360° polarization angle.The structure of the absorber is relatively simple,the absorption broadband can be adjusted,and it can be adjusted in a wide range from multiple angles,so the application value is high.