Design of a Graphene-Based Multi-Band Metamaterial Perfect Absorber with Polarization-Insensitive Ability for Terahertz Applications

This paper presents a graphene-based polarization-insensitive metamaterial perfect absorber at terahertz frequency range. The absorber consists of a graphene pattern layer at the top of the structure, a dielectric spacer layer, and an Au layer at the bottom of the structure. In the proposed structure, the ability of perfect absorption is investigated by the complete suppression of radiation and reflected light and the complete dissipation of incident energy. At the first, the proposed structure and its design process are verified and it is shown that in the three bands, the results of perfect absorption at frequencies of 2, 2.95 and 3.75 terahertz are achieved with absorption rates of 93.5%, 99.8% and 98.1%, respectively. Also, the physical mechanism of structure performance is investigated by the surface distribution of the electric field, as well as the geometric changes of the structure. In addition, the design of the proposed structure with graphene provides this advantage so that the resonant frequency can be adjusted by changing the Fermi energy level and graphene relaxation time without changing the proposed structure again. With the study, it is found that the proposed metamaterials perfect absorber is not sensitive to polarization and is more tolerant to the angle of incident radiation. Accordingly, the proposed broadband absorber in this paper has potential in imaging, detection, filtering, solar tracking and other applications.