A metamaterial broadband absorber by tuning single graphene material for various terahertz domain applications

A broadband metamaterial-based absorber (MTMA) with a broad absorptance response is proposed in this research article, which contains a straightforward structure with three layers namely lossy silicon functioning as a dielectric medium, copper as a bottom conductive layer, and finally graphene-based top layer as a radiating patch. The geometry of the MTMA consists of an octagon-shaped patch surrounded by a rectangular strip-connected square-type ring. The lossy silicon is the dielectric material, with a thickness (d) of 4 μm. The ground (bottom) conductive layer is of copper having 0.1 μm thickness (tg) and a conductivity (σ) of 5.9 × 10⁷ s/m. At a temperature of 300° Kelvin, graphene material with a thickness of 1 nm is used for the proposed absorber. Moreover, it possesses a polarization-insensitive (PIS) nature. A broad spectrum with >90 % absorptance is obtained by fixing the graphene material's chemical potential to 0.7 eV (eV) and the relaxation time to 0.1 ps. The design of MTMA possesses straightforward construction without having multiple dielectric or conductive layers. It provides an excellent absorptance near unity (99 %) over the operating frequency range with a compact size of 2.5 × 2.5 × 4 μm³. It achieves an absorptance bandwidth of 3.26 THz within the terahertz domain covering a broad spectrum from 8.20 to 11.46 THz. The structure produces the same absorptance bandwidth irrespective of changes in polarization angle. Additionally, the proposed configuration is validated using an equivalent electrical circuit (ECC) model with the help of the ADS tool. The exclusive behavior of the propounded absorber in the terahertz band points to possible applications in various terahertz-based devices for spectroscopy, energy harvesting, high-speed wireless communications, food processing, detection, imaging, and sensing, etc.