Graphene-based polarization insensitive ultrathin broadband terahertz absorber for material sensing applications

Abstract

In this paper, a tunable broadband electromagnetic absorber for sensing applications at terahertz frequencies is proposed. The proposed design consists of a graphene based multiple slot loaded rectangular resonator, dielectric material and gold based metallic ground plane. The dimensions of proposed absorber’s unit cell are 10 μm × 10 μm. The proposed absorber has more than 90% absorption over a frequency spectrum of 4.86–18.33 THz (% fractional bandwidth > 116.22%). The proposed absorber is symmetric which makes the structure polarization insensitive. It has stable characteristics for incidence angle (θ) ≥ 40∘ for both Transverse-Electric (TE) and Transverse-Magnetic (TM) waves. The effects of different substrate materials, different analyte materials, variations in the graphene parameters and water level on the proposed absorber’s performance are also analyzed. This absorber can be used to detect different materials including water and thickness of water layer present on its top surface. The proposed graphene-based absorber dominates previously reported wideband THz absorbers in terms of relative bandwidth, more than 90% absorption peak values, oblique stability and overall volume.