Electrically Tunable Broadband Terahertz Absorption with Hybrid-Patterned Graphene Metasurfaces.

Longfang Ye,Jinfeng Zhu,Na Liu,Guoxiong Cai,Qing Liu,Xin Chen

doi:10.3390/nano8080562

Longfang Ye, Jinfeng Zhu + Show 4 more

Open Access

https://doi.org/10.3390/nano8080562

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Abstract

We numerically demonstrate a broadband terahertz (THz) absorber that is based on a hybrid-patterned graphene metasurface with excellent properties of polarization insensitivity, wide-angle, and active tunability. Our design is made up of a single-layer graphene with periodically arranged hybrid square/disk/loop patterns on a multilayer structure. We find that broadband absorption with 90% terahertz absorbance and the fractional bandwidth of 84.5% from 1.38 THz to 3.4 THz can be achieved. Because of the axisymmetric configuration, the absorber demonstrates absolute polarization independence for both transverse electric (TE) and transverse magnetic (TM) polarized terahertz waves under normal incidence. We also show that a bandwidth of 60% absorbance still remains 2.7 THz, ranging from 1.3 THz to 4 THz, for a wide incident angle ranging from 0° to 60°. Finally, we find that by changing the graphene Fermi energy from 0.7 eV to 0 eV, the absorbance of the absorbers can be easily tuned from more than 90% to lower than 20%. The proposed absorber may have promising applications in terahertz sensing, detecting, imaging, and cloaking.

Highlights

With the rapid development of terahertz technology, terahertz absorbers have attracted increasing attention in recent years [1]
The broadband terahertz surface plasmon resonance absorption will be enhanced by this patterned graphene sheet
It is observed that lossy dielectric spacers with tan δ ≤ 0.01 only result in a negligible absorbance enhancement. This is because the EM fields are extremely confined around the graphene layer, and almost all terahertz absorption results from the graphene layer

Summary

Introduction

With the rapid development of terahertz technology, terahertz absorbers have attracted increasing attention in recent years [1]. Absorbers with periodic arrays of metallic square ring/cross/hash-shaped resonators, circular split rings, combined metamaterial structures, 3D TiN nanopillars, and all-dielectric metasurfaces were proposed to achieve single narrowband, dual/multi-narrowband, and broadband perfect absorption [3,7,8,9,10,11,12,13,14,15]. We propose a novel absorber that is made up of a single-layer periodically hybrid-patterned graphene on a multilayer structure for wide-angle and polarization-insensitive broadband terahertz absorption with flexibly active tunability. The proposed absorber may have promising applications in terahertz sensing, detecting, imaging, and cloaking

The Absorber Design

Results and Discussion

Conclusions