Design of multifunctional metamaterial absorber based on electro-optic properties of graphene

Abstract

Recently, metamaterial absorber has attracted considerable attention because of a broad range potential application to electromagnetic stealth, electromagnetic detectors, and electromagnetic communication. In this paper, a multifunctional metamaterial absorber based on the electro-optic properties of grapheme is presented. The absorber was consisted of graphene microstructure, PDMS media layer and a single layer ITO film. These components made the absorber is optically transparent because all of the components are optically transparent. At first, we optimized the structural parameters to get a satisfactory absorption rate by the finite element method when the Fermi level of graphene was 0.5 eV. In this process, we found the resonance frequency of the absorber will have a red shift phenomenon with the increase of the dielectric layer thickness. When the dielectric layer thickness increases from 1.3 to 1.6 mm, the resonance frequency of the absorber is red-shifted from 84 to 67 GHz. And the absorption rate was almost unchanged in this process. Secondly, we mainly simulated the influence of Fermi level of graphene on the absorption characteristics of absorber by the same method when the dielectric layer thickness was 1.5 mm. The research indicated that the absorber possessed a amplitude tunable characteristic resulting from the change of grapheme Fermi level by altering the applied voltage. When the graphene Fermi level increased from 0 to 0.5 eV, the absorption rate of the absorber would from 50% to 97%. And the simulation results showed that the bandwidth achieves 8.2 GHz for the absorption beyond 90%, and the maximum absorption is up to 97% when the graphene Fermi level is 0.5 eV and the dielectric layer thickness was 1.5 mm. In addition, we proved the absorber is insensitive to the polarization and the wide-angle. The absorption rate would not change when we changed the polarization direction or changed the incident angle within 45°. Finally, we studied the distribution of the surface current and the electric field to explore the physical mechanism of electromagnetic wave absorption and amplitude adjustment by simulation method. In summary, the research indicated the absorber not only has the ultra-high electromagnetic wave absorptivity of traditional metamaterial absorbers, but also has the functions of optically transparency and amplitude adjustable. And it had potential application value in the fields of electromagnetic stealth, electromagnetic detectors, and electromagnetic communication.