Design Of Tunable Absorbers Based On The Graphene Metamaterials

Electromagnetic metamaterials have many characteristics that natural materials do not have.Their electromagnetic parameters such as dielectric constant and permeability can be tuned by changing the internal unit structure.Therefore,electromagnetic metamaterials have broad application prospects in the fields of electromagnetic stealth,super lens and so on.Graphene has become a research hotspot in many fields once it is found because of its unique physical properties,especially electrically adjustable properties.When graphene is patterned,the wave incident on the surface of graphene can excite surface plasmon resonance at the edge of graphene,so that the energy is bound near the microstructure of graphene.Based on the theory of metamaterial and graphene,two kinds of metamaterial absorbers are designed,and their performances are analyzed using the simulation software.Firstly,a broadband absorber in terahertz range is studied.The surface plasmon of graphene induces the generation of the Fabry-Perot resonance.The broadband absorption of 3.12 THz is obtained,and the maximum absorption is 0.999,realizing perfect absorption.On the premise of not changing the structural parameters,the absorption rate and absorption band of the absorber can be dynamically controlled by changing the chemical potential of graphene.When the chemical potential of graphene is 0 eV,that is,when graphene is not regulated,the reflectivity of the absorber is as high as 0.84,which can be used as a reflector.Secondly,a bifunctional absorber,whose working mode conversion is realized by using the thermal tuning characteristics of vanadium dioxide,is studied.At room temperature of 23?,that is,when the conductivity of vanadium dioxide is 10 S/m,the vanadium dioxide shows dielectric characteristics.The absorber works in multi-band mode,and the absorption curve consists of three frequency bands:0.67 THz?1.58 THz,3.41 THz?3.60 THz and 4.01 THz?5.12 THz with amaximum absorption rate of 0.984.When the temperature rises above 68?,that is,when the conductivity of vanadium dioxide is 200000 S/m,the vanadium dioxide shows metal characteristics.The absorber works in broadband mode,with a working band of 2.62 THz?5.94 THz,and its absorption bandwidth is 3.32 THz and the maximum absorption is 0.979.The transformation of vanadium dioxide from dielectric state to metal state can be realized by heating the temperature up to 68?.This phase transition temperature is relatively low and has good operability.