A graphene-based dual-band THz absorber design exploiting the impedance-matching concept
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S.I. : T WO-DIMENSIONAL MATERIALS
A graphene‑based dual‑band THz absorber design exploiting the impedance‑matching concept Sadegh Biabanifard1 Received: 24 March 2020 / Accepted: 12 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A THz wave absorber is designed by exploiting a unique concept and method. Three layers including dielectric and graphene patterns are incorporated on top of a thick gold surface to ensure zero transmission of THz waves through the structure. A favorable dual-bias scheme is used for the periodic arrays of graphene ribbons in the first layer, while the second layer consists of periodic arrays of graphene disks. Also, a top layer consisting of a continuous graphene sheet is used to enhance the overall absorption. All the components are modeled via a circuit model approach developed based on passive circuit elements. This leads to an explicit impedance calculation for the structure, paving the way to fully predict the device behavior. By applying impedance-matching theory, the structural parameters are tuned to obtain perfect dual-band absorption at frequencies of 5.5 and 8.5 THz. Extensive simulations verify the robustness of the structure versus variations in its geometrical parameters, while a great ability to tune the absorption peaks is achieved via variation of the chemical potentials. Such robust and tunable absorbers are attractive for the design of optical sensors, detectors, and modulators. Keywords Graphene · Absorber · THz · Circuit model · Transmission-line theory
1 Introduction In recent years, terahertz technology has attracted considerable attention for use in telecommunications engineering due to its critical role in many applications such as sensors, biosensing, imaging, internal telecommunications, medicine, and surgery. High practical frequency, reduced size, low photon energy, and excellent performance are some of the advantages of using the terahertz part of the spectrum. Moreover, the ongoing growth of nanotechnology in various scientific and industrial areas alongside the introduction of new materials such as graphene has expanded use of the terahertz part of the spectrum (ranging from approximately 100 GHz to 10 THz), representing a potential area for modern plasmonic devices that offer high quality and high efficiency. Graphene is a two-dimensional semimetallic material composed of a layer of carbon atoms in a honeycomb lattice arrangement and offering excellent optical, electrical, and physical properties. Besides, compared with noble metals
* Sadegh Biabanifard [email protected] 1
Iran Analog Research Group, Tehran, Iran
such as gold and silver, graphene exhibits better plasmonic properties in the terahertz part of the spectrum. Also, the ability to adjust the surface conductivity of graphene by manipulating its Fermi energy through chemical injection or electrical biasing offers good potential for understanding the tunability and flexibility in practice. Besides, due to the requirement for terahertz ab
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