Design of a broadband and polarization insensitive THz absorber based on two layers of periodic arrays of graphene disks

TL;DR

This paper presents an analytical design for a broadband, polarization-insensitive THz absorber using two layers of graphene disks, achieving over 90% absorption and a 75.4% normalized bandwidth, validated by FEM and CST simulations.

Contribution

The paper introduces a simple, two-layer graphene disk structure for broadband THz absorption with high efficiency and polarization insensitivity, validated through analytical and numerical methods.

Findings

Absorption exceeds 90% at the central frequency.

Normalized bandwidth reaches 75.4% in 5 THz.

Analytical design matches well with FEM and CST simulations.

Abstract

In this paper, we analytically design a simple configuration of a broadband THz and polarization-insensitive absorber. The mentioned absorber consists of two layers of graphene disks, and the transmission line model is considered for the whole of the proposed absorber's structure to design it accurately. Therefore, the input admittance of the designed absorber is obtained by the transmission line model. Also, the real part of the input admittance is approximately tuned to be matched to the free space admittance. In contrast, the imaginary part of it is closely adjusted to zero around the central frequency of the THz absorber. Using only just two layers of Periodic Arrays of Graphene Disks (PAGDs) with one kind of dielectric as the material of substrates, it causes that the absorption of the structure can be achieved higher than 90 % by the Finite Element Method (FEM). Normalized bandwidth has reached up to 75.4% in 5 THz as the central frequency of the device. As the next step, we use the CST studio software to validate our designed absorber, and it will show that the numerical results will have the best matching with the analytical method.