Polarization-Insensitive Broadband THz Absorber Based on Circular Graphene Patches.

Jiajia Qian,Shuting Wu,Zhenzhen Ge,Jun Zhou,Xiaoming Liu,Zheng Zhu,Jian Yi

doi:10.3390/nano11102709

Abstract

A polarization-insensitive broadband terahertz absorber based on single-layer graphene metasurface has been designed and simulated, in which the graphene metasurface is composed of isolated circular patches. After simulation and optimization, the absorption bandwidth of this absorber with more than 90% absorptance is up to 2 THz. The simulation results demonstrate that the broadband absorption can be achieved by combining the localized surface plasmon (LSP) resonances on the graphene patches and the resonances caused by the coupling between them. The absorption bandwidth can be changed by changing the chemical potential of graphene and the structural parameters. Due to the symmetrical configuration, the proposed absorber is completely insensitive to polarization and have the characteristics of wide angle oblique incidence that they can achieve broadband absorption with 70% absorptance in the range of incident angle from 0° to 50° for both TE and TM polarized waves. The flexible and simple design, polarization insensitive, wide-angle incident, broadband and high absorption properties make it possible for our proposed absorber to have promising applications in terahertz detection, imaging and cloaking objects.

Highlights

Terahertz (THz) [1] wave usually refers to the electromagnetic wave in the frequency range of 0.1–10 THz
The surface conductivity σ of graphene is composed of two parts: the conductivity σintra contributed by the electron photon scattering in the band and the conductivity σinter contributed by the interband transition of carriers, and it can be expressed by Kubo formula when the magnetic field is neglected [53,54], σintra (ω, μc, Γ, T ) =
To study the broadband absorption properties of THz, three different graphene patterns were simulated, including a graphene circular patch located only at the center of square unit cell, quarter of graphene circular patches located at the four vertices of square unit cell and the structure proposed in this paper combined the above two

Summary

Introduction

Terahertz (THz) [1] wave usually refers to the electromagnetic wave in the frequency range of 0.1–10 THz (wavelength of 3 mm to 30 μm). A series of recent breakthroughs have helped to bridge this gap [2,3], to the point that nowadays it is a field of intense and multidisciplinary research with many applications coming into reality in numerous sectors, like chemistry, biomedicine, astronomy, national defense, security inspection, remote sensing and wireless communications [4,5,6,7,8,9] The focus on this spectrally rich region is attributed to the highly coherent and non-ionizing nature of THz radiation, wide unallocated frequency bands, distinctive wavelengths and their penetration through a significant depth of dielectric materials. THz devices such as splitters, filters, absorbers, modulators, encoders, switches, polarizers and lens have been studied

Methods

Results

Conclusion