Design And Research Of Metamaterial Absorber

Metamaterials are artificial materials with nano-structures,which are unattainable in nature possessing exotic optical properties and providing a new way to manipulate light in subwavelength scale.During the last decade,metamaterials have attracted considerable attention and many astonishing optical properties such as negative refraction,cloaking and super lens are observed.Meanwhile,many novel functional devices based on metamaterials are proposed and they cover all the technical frequencies ranging from microwave to optical region.Recently,metamaterial absorbers(MA)have attracted considerable interest due to the merits of compact structures,prefect absorption and easily tunable resonances.By properly designing the structure of the MA unit,the resonance of surface plasmon polarization can be efficiently excited,resulting in perfect light absorption at sub-wavelength scale.Major aspects of the work are as follows:(1)An independently tunable coherent perfect multiband Graphene metamaterial absorber,composed of four layers in the middle of structure surrounded by the zinc sulfide dielectric,is proposed and investigated in the mid-infrared region.When two beams of coherent light are projected on the absorber,we can use one beam to control the absorption,reflection and transmission of another beam.The results reveal that the absorption spectrum of the graphene metamaterial absorber structure displays four perfect absorption peaks in the mid-infrared region,corresponding to the absorption value of 99.2% at 6.73 um,99.9% at 7.032 um,99.8% at 7.28 um and 97.6% at 7.6833 um,respectively.Conductivity of graphene is adjusted by the Fermi level,while the Fermi level is controlled by bias voltage over the graphene.So we can adjusted graphene's conductivity to control the resonant frequency of the absorber.(2)A wide-angle,broadband,perfect metamaterial absorber is composed of a periodical array of unit cells with four sub atom of graphene is presented and studied.The structure of the unit cell is metal-dielectric 1-dielectric 2-metals.The structure is designed according to the concept that the metamaterial absorber's resonant frequency can be tuned by adjusting the filling factor of sub atom structure over the base-insulator.The calculated results reveal that the structure has four perfect absorption peaks in the terahertz frequency band.The related absorption bandwidth is 300 GHz and the average absorptivity is 98.6%.At the same time,the structure is insensitive to the incident angel.When the incident angle is less than 70°,the absorption rate is over 90%.