Study On Tunable Electromagnetic Metamaterial Absorber Based On Graphene

As a new type of artificial composite material,subwavelength electromagnetic metamaterials possess special physical properties that traditional materials do not possess.With the development of nanotechnology,subwavelength electromagnetic metamaterials have made remarkable achievements in electromagnetic wave absorption,electromagnetic stealth and surface electromagnetic enhancement.Generally speaking,the electromagnetic metamaterial absorber is composed of three parts: the metal reflection layer,the intermediate medium layer and the patterned surface layer that prevent light transmission.It is found that the absorption rate and frequency band of the metamaterial absorber are related to the thickness of the medium layer and the shape and size of the surface layer.Although absorbers of different frequency bands can be designed by changing the above structural parameters,once such absorbers are formed,the absorption frequency band cannot be changed and the absorption rate cannot be adjusted,which leads to great limitations of absorbers in optical applications.Therefore,it is necessary to study the absorbers with adjustable frequency band and dynamic adjustable absorption rate.Graphene is a kind of two-dimensional nanometer material with hexagonal distribution of carbon atoms in the same plane.Its conductivity can be effectively changed by doping and applied voltage.Therefore,the study of electromagnetic metamaterial absorbers with tunable absorption frequency band based on graphene materials has become a hot topic in the field of light absorption.At present,the electromagnetic metamaterial absorber based on graphene research has made great progress,but there are disadvantages such as single regulation means,complex structure and low efficiency,based on this,this paper puts forward a kind of simple structure,through the applied voltage can be implemented to take to bring even more broadband,absorption rate near perfect absorption can be tuned absorber.On this basis,we further studied a coherent photographene metamaterial absorber with tunable absorptivity and absorption band.Specific research contents can be divided into the following two aspects:1.A disc-shaped graphene metamaterial electroregulatory absorber containing gold electrodes.The absorber consists of two graphene disks with different radii and a gold electrode attached to them.The voltage is applied directly to each graphene disk through a gold electrode,allowing the Fermi energy in each graphene disc to be independently regulated.The simulation results show that the dual-frequency,multi-frequency and broadband absorption characteristics can be dynamically tuned through the combination of different Fermi energies on the graphene disk.In addition,due to the influence of the gold electrodes on the graphene disks,the absorption rate can be as high as 95% in the dynamically adjustable band,which avoids the disadvantage of the significant decrease in the absorption rate in other graphene absorbents due to the change of the above conditions.At the same time,due to the symmetry of the structure,the proposed absorber is polarization-independent and can work in a wide range of incident angles.2.Based on the principle of coherent absorber,we further designed a coherent tunable electromagnetic metamaterial absorber composed of double layer cruciform graphene.First of all,we study the dual frequency and multi-frequency absorption of the absorber.On this basis,the wide band absorption of the absorber is realized through the design of two cross-shaped sizes.We then studied the relationship between the movement of the absorption band and the change of the graphene Fermi energy,showing the dynamic tunable performance of the absorber in different frequency bands.Then the absorption rate is dynamically adjusted by phase adjustment of coherent light.Due to the symmetrical cruciform structure,the absorber is insensitive to polarization.Due to its simple structure,wide frequency band,adjustable absorption rate and absorption band,the absorber has potential application value in light absorption modulator,light switch and so on.