Dual-band terahertz absorber based on graphene periodic arrays of disks and ribbons: circuit model approach
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Dual‑band terahertz absorber based on graphene periodic arrays of disks and ribbons: circuit model approach Toktam Aghaee1 · Ali A. Orouji1 Received: 29 March 2020 / Accepted: 25 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A dual narrow band perfect THz absorber is presented in this work. The structure includes three layers of graphene ribbons, disks, and sheet on the TOPAS dielectric layer while a golden plate is placed at the bottom to act as a fully reflecting mirror against THz waves. According to the simulations, the device is robust enough to show independent operation versus layers thicknesses variations, chemical potentials mismatches, and changing of electron relaxation time. The designed THz absorber in this work is an appropriate basic block for several applications in THz optical systems such as sensors, detectors, and modulators. The layers in the proposed device are modeled via passive circuit elements and consequently, the equivalent circuit of the device is calculated. Leveraging developed circuit model and impedance matching concept, the proposed device is designed to perfect absorption at 1 THz and 7 THz. Ample simulations are performed using MATLAB and CST to verify the superior performance of the device. The presented manuscript considers the circuit model representation for three different layers of the device. For a unique structure, highly tunable response versus chemical potential is obtained. Circuit model approach and impedance matching theory are exploited to reduce computational time regarding conventional approaches. Keywords Graphene · Circuit model · Dual-band · THz · Absorber · Thin film
1 Introduction Recently, graphene-based absorbers have attracted the attention of many researchers in the field of electronics and telecommunications engineering. Graphene, a material with many properties in optical applications, composed of carbon atoms with a honeycomb structure that extends from end to end [1]. The graphene bandgap situation is such that in some places known as Dirac points, the distance between the conduction band and the valance band is approximately zero [2]. This feature has made graphene, unlike other semiconductors that require energy to move electrons from the valance band to the conduction band [3]. But studies of graphenebased materials have not been completed, and new behavior of graphene material has been observed against a wave that radiates to its surface, with electrons moving around the orbits on the graphene surface [4]. So that when a wave hits the graphene surface, the electrons move around the * Ali A. Orouji [email protected] 1
Electrical Engineering Department, Semnan University, Semnan, Iran
orbit, and they do not get out of that orbit unless they hit a phonon [5]. Different forms of graphene have been presented so far, the most prominent of which are carbon nanotubes, 3D graphene, graphene nano-ribbons, and graphene-oxygen blends. Graphene is also used to control nanoscale light emission [6]. Resea
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