Numerical Analysis and Circuit Model of Tunable Dual-Band Terahertz Absorbers Composed of Concentric Graphene Disks and
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https://doi.org/10.1007/s11664-020-08336-y 2020 The Minerals, Metals & Materials Society
Numerical Analysis and Circuit Model of Tunable Dual-Band Terahertz Absorbers Composed of Concentric Graphene Disks and Rings MONA ARABMOHAMMADI,1 ZAHRA GHATTAN KASHANI and RAMEZAN ALI SADEGHZADEH SHEIKHAN1
,1,2
1.—Faculty of Electrical Engineering, K. N. Toosi University of Technology, Tehran, Iran. 2.—e-mail: [email protected]
In this paper, periodic arrays of concentric graphene disks and rings placed near a metallic ground coated by a dielectric substrate are proposed and analyzed by a circuit model approach (CMA) to predict the absorption of the structure in the terahertz (THz) region. As numerical examples, single-band absorbers composed of graphene disks or graphene rings and a dual-band absorber composed of both graphene disks and rings are designed, presented, and proposed. In order to validate the accuracy of the results achieved by the CMA, numerical simulations based on the finite integral technique are applied. One of the significant features of the proposed structures is the tunability of the position of the absorption peak by controlling the chemical potential of the graphene patterns. An additional advantage of the proposed absorbers is that the absorption peaks of the dual-band absorber are stable for both transverse magnetic and transverse electric polarization with incident wave angles up to 70. The proposed absorber could be used as an essential element in real-time THz detection and sensing systems. Key words: Terahertz, graphene disks and rings, dual-band, tunable absorber, circuit model approach, FIT numerical simulation
INTRODUCTION Surface plasmon polaritons (SPPs) are sub-wavelength electromagnetic waves propagating at the interface between a metal and a dielectric material. They have recently attracted wide interest and attention.1 With the use of SPP waves, plasmonic devices such as logic gates,2,3 demultiplexers,4,5 and sensors6,7 have been proposed and investigated. Poor confinement of the incident light wave, difficulty in controlling the permittivity, and high losses are the drawbacks of plasmonic metallic structures and devices.
(Received January 18, 2020; accepted July 14, 2020)
Graphene is a single layer of carbon atoms with considerable optical specifications.8,9 Graphene SPPs have shown better performance compared to metal SPPs, such as field confinement,10 long propagation length,11 and tunability.12 Various types of plasmonic graphene-based devices have recently been proposed, investigated, and analyzed, including multi/demultiplexers,13,14 filters,15,16 sensors,17,18 logic gates,19,20 and absorbers.21,22 Circuit modeling analysis was used in Refs. 23–26 without any numerical calculation support. Here, we report a general circuit model approach (CMA) for the design of graphene-based single- and dual-band absorbers, which could be applied to any other multiband absorbers. It is possible to tune the resonance frequencies and the absorption bands of the proposed THz absorber by c
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