A Polarization-Insensitive and Wide-Angle Terahertz Absorber with Ring-Porous Patterned Graphene Metasurface.

Hongyang Shen,Dong Zeng,Fengxiang Liu,Xuguang Huang,Chunyang Liu,Faqiang Wang,Banghong Guo,Hongyun Meng,Chunhua Tan,Zhongchao Wei

doi:10.3390/nano10071410

Abstract

A broadband terahertz (THz) absorber, based on a graphene metasurface, which consists of a layer of ring-porous patterned structure array and a metallic mirror separated by an ultrathin SiO2 dielectric layer, is proposed and studied by numerical simulation. The simulated results show that the absorptivity of the absorber reaches 90% in the range of 0.91–1.86 THz, and the normalized bandwidth of the absorptivity is 68.6% under normal incidence. In the simulation, the effects of the geometric parameters of the structure on the absorption band have been investigated. The results show that the absorber is insensitive to the incident polarization angle for both transverse electric (TE) and transverse magnetic (TM) under normal incidence. In addition, the absorber is not sensitive to oblique incidence of the light source under TE polarization conditions, and has an approximately stable absorption bandwidth at the incident angle from 0° to 50°. The absorption band can be adjusted by changing the bias voltage of the graphene Fermi level without varying the nanostructure. Furthermore, we propose that a two-layer graphene structure with the same geometric parameters is separated by a dielectric layer of appropriate thickness. The simulated results show that the absorptivity of the two-layer absorber reaches 90% in the range of 0.83-2.04 THz and the normalized bandwidth of the absorptivity is 84.3% under normal incidence. Because of its excellent characteristics based on graphene metamaterial absorbers, it has an important application value in the field of subwavelength photonic devices.

Highlights

The area between the far infrared and the ultra-microwave is terahertz (THz), whose frequency ranges from 0.1 to 10 THz
It is very beneficial to study the novel graphene-type terahertz absorber with a wide absorption band, as well as polarization insensitivity, multi-angle incidence, and tunability
We propose a polarization-independent and wide-angle absorber based on a graphene metasurface at terahertz frequencies, which consists of a graphene array structure with ring-porous patterns, a dielectric layer and a metal layer to achieve a high-bandwidth absorption

Summary

Introduction

The area between the far infrared and the ultra-microwave is terahertz (THz), whose frequency ranges from 0.1 to 10 THz. To obtain a wide absorption, multi-layer graphene/metal coupled metamaterial absorbers have been proposed [11,12,13,14].

Results

Conclusion