Wednesday, April 8, 2020

Abstract-Tunable multi-band terahertz absorber using a single-layer square graphene ring structure with T-shaped graphene strips


Kai-Da Xu, Jianxing Li, Anxue Zhang, and Qiang Chen


(a) Perspective view and (b) top view of the proposed graphene-based dual-band terahertz absorber. The parameters w1 and a are the widths and side lengths of the square graphene ring, respectively. The parameters w2l1 and l2 represent the width and two distinct lengths of the T-shaped graphene strips, respectively. d and dg are the thicknesses of the spacer layers (Topas) and metal ground plane (gold), respectively. The symbol p is the periodicity of the periodic absorber structure. These parameters are set as: w1=0.155 µm, w2=0.12 µm, l1 = 0.26 µm, l2= 1.1 µm, a=2.6 µm, p=4 µm, d=18 µm, and dg=1 µm.
(a) Absorption spectra of the traditional square graphene ring periodic array, only four T-shaped graphene strips periodic array, and proposed periodic array under normal TE and TM incident waves with the identical parameters (illustrated in Fig. 1). (b) Absorption spectra of the proposed periodic array for varied polarization angles.
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-8-11482

We numerically demonstrate a tunable dual-band terahertz metamaterial absorber (MA) with near-unity absorption using single-layer square graphene ring structure with T-shaped graphene strips. By periodically loading four T-shaped graphene strips to the square graphene ring periodic array without additionally increasing the size of MA device, the pre-existing resonant frequency will have a red shift and simultaneously a new resonance will be generated at higher frequency for achieving a dual-band MA. The two absorption peaks can be tuned to the resonant frequencies of interest by varying the parameters of the square graphene ring and T-shaped graphene strips. The operating frequency of the absorption spectrum can be also manipulated by adjusting the chemical potential of graphene, without changing their geometric parameters. Additionally, numerical results show that the proposed MA possesses polarization-independent and incident-angle-insensitive properties. To further extend the proposed structure’s application with more absorption peaks, a tri-band MA is investigated through adding four more T-shaped graphene strips based on the dual-band absorber configuration. Therefore, our research work will be a good candidate for the design of various graphene-based tunable multi-band absorbers at different frequency regions with potential applications in optoelectronic devices and systems.
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