Broadband absorber with periodically sinusoidally-patterned graphene layer in terahertz range

Longfang Ye,Na Liu,Zhengyong Song,Jinfeng Zhu,Qing Huo Liu,Guoxiong Cai,Yao Chen

doi:10.1364/oe.25.011223

Abstract

We demonstrate that a broadband terahertz absorber with near-unity absorption can be realized using a net-shaped periodically sinusoidally-patterned graphene sheet, placed on a dielectric spacer supported on a metallic reflecting plate. Because of the gradient width modulation of the unit graphene sheet, continuous plasmon resonances can be excited, and therefore broadband terahertz absorption can be achieved. The results show that the absorber's normalized bandwidth of 90% terahertz absorbance is over 65% under normal incidence for both TE and TM polarizations when the graphene chemical potential is set as 0.7 eV. And the broadband absorption is insensitive to the incident angles and the polarizations. The peak absorbance remains more than 70% over a wide range of the incident angles up to 60° for both polarizations. Furthermore, this absorber also has the advantage of flexible tunability via electrostatic doping of graphene sheet, which peak absorbance can be continuously tuned from 14% to 100% by controlling the chemical potential from 0 eV to 0.8 eV. The design scheme is scalable to develop various graphene-based tunable broadband absorbers at other terahertz, infrared, and visible frequencies, which may have promising applications in sensing, detecting, and optoelectronic devices.

Highlights

Broadband terahertz absorbers have recently attracted increasing interests for their promising applications in terahertz trapping [1,2], sensing [3,4], imaging [5,6], and detecting [7]
By controlling the chemical potential via electrostatic doping of the graphene sheet, the peak absorbance can be continuously tuned from 14% to 100%
Broadband terahertz absorption is obtained for both polarizations

Summary

Introduction

Broadband terahertz absorbers have recently attracted increasing interests for their promising applications in terahertz trapping [1,2], sensing [3,4], imaging [5,6], and detecting [7]. To enhance the light confinement and transform this poorly absorbing graphene into a perfect absorber, various graphene absorbers with periodic structures including arrays of disks [8,11], ribbons [19,20,21], cross-shaped structures [22], as well as graphene and metal combined structures [23] have been proposed. These absorbers relying on the resonant structures of unit cells are usually very narrowband, which greatly limits their further applications in optoelectronic devices

Methods

Results

Conclusion