Broadband near-perfect terahertz absorber in single-layered and non-structured graphene loaded with dielectrics

In this work, we have done an extensive study on broadband near-perfect absorbers consisting of single-layered and non-structured graphene loaded with periodical arrays of dielectric bricks, including square and elliptical bricks. We also propose and investigate circular cylinder, rectangular brick, and racecourse dielectric structure. Moreover, the calculated z component of the electric field enables us to understand the physical mechanism of resonance absorption. Furthermore, we also studied and proposed a new absorber with periodical arrays of stepped rectangle dielectric structure. We could achieve a broadband absorption from 1.6 to 4.2 THz, with a bandwidth of 2.6 THz and absorption over 90%. The proposed absorber is also tunable; the tunability of the terahertz (THz) broadband absorber is achieved via changing the external gate voltage to modify the Fermi energy of graphene. Also, we compared the results and absorption spectra of different dielectric structures. This THz metamaterial structure can be used in different THz applications such as cloaking, sensing, detection, and imaging. (C) 2020 Optical Society of America