Independently tunable dual-band perfect absorber based on graphene at mid-infrared frequencies.

Yuping Zhang,Huiyun Zhang,Tongtong Li,Ethan Abele,Antoinette J Taylor,John F O’Hara,Abul K Azad,Qi Chen,Hou-Tong Chen

doi:10.1038/srep18463

Abstract

We design a dual-band absorber formed by combining two cross-shaped metallic resonators of different sizes within a super-unit-cell arranged in mirror symmetry. Simulations indicate that absorption efficiencies greater than 99% can be achieved at two different frequencies under normal incidence. We employ a design scheme with graphene integration, which allows independent tuning of individual absorption frequencies by electrostatically changing the Fermi energy of the graphene layer. High absorbance is maintained over a wide incident angle range up to 50 degrees for both TE and TM polarizations. It thus enables a promising way to design electrically tunable absorbers, which may contribute toward the realization of frequency selective detectors for sensing applications.

Highlights

The schematic design of the proposed tunable metamaterial absorber is illustrated in Fig. 1(a), and it consists of a traditional metamaterial absorber architecture with metallic resonators separated from a ground plane by a dielectric spacer
By optimizing the thickness of the spacer ts = 0.285 μ m, we obtained two absorption bands with peaks absorbance greater than 99%
90% absorbance is still obtained at large incidence angles for both of the two resonance peaks under TE and TM polarizations We have investigated the incident angle-dependent absorbance for various Fermi energies and have not observed any Fermi energy related discontinuity in the absorption bands that were noticed in earlier demonstration[33]

Summary

Introduction

Vg1 and Vg2, are applied to the two graphene interdigitated finger sets in order to tune their Fermi energies independently. We first investigated a dual-band metamaterial absorber shown in Fig. 1 except that the graphene layer is uniform over the entire sample. Varying Ef from 0.2 eV to 0.8 eV, which could be accomplished by applying a voltage bias between the ground plane and graphene layer, both absorption peaks show blue-shift while the high absorbance is remained.

Results

Conclusion