Electrical Manipulation of Electromagnetically Induced Transparency for Slow Light Purpose Based on Metal-Graphene Hybrid Metamaterial

Chenxi Liu,Peiguo Liu,Cheng Yang,Qihui Zhou,Song Zha

doi:10.3390/app8122672

Chenxi Liu, Peiguo Liu + Show 3 more

Open Access

https://doi.org/10.3390/app8122672

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Abstract

A terahertz metamaterial is presented and numerically investigated to achieve tunable electromagnetically induced transparency (EIT) for slow light. The unit cell consists of cut-wire pairs and U-shaped ring resonators with graphene strips placed between the metal film and the SiO2/Si substrate. Through bright-dark mode coupling, the radiative resonance induced by the U-shaped ring is suppressed, and then the typical EIT effect is realized. The transparency window and the accompanied group delay can be electrically manipulated with different Fermi energy of the graphene. By analyzing the surface distribution, the underlying tuning mechanism of this hybrid metamaterial is investigated in detail. Moreover, the transparency peak decreases slightly with the increasing strip width of the graphene layer but completely vanishes as the strip width exceeds the length of the covered U-shaped ring. The influence of the critical index of graphene quality, i.e., carrier mobility on the EIT effect, is considered. The results of this study may provide valuable guidance in designing and analyzing tunable EIT structures based on a metal-graphene hybrid structure for slow light purposes.

Highlights

The past decade has witnessed great developments in the artificially engineered material metamaterial, which has attracted extensive interests due to its unique electromagnetic properties [1].Tailored in diverse architectures, metamaterials provide opportunities to control the electromagnetic wave in a wide range, from microwave to near-infrared regions [2,3,4]
We present a metal-graphene hybrid metamaterial composed of metal cut-wires and U-shaped rings as well as graphene strips
In order to explore the response of the hybrid metamaterial, the numerical calculations are lower-THz region is dominated by the intraband transitions, which can be expressed using the performed based on the frequency domain method and employing the electromagnetic simulation well-known Kubo formula [25]: software CST Microwave Studio based on the frequency domain Finite Element Method

Summary

Introduction

The past decade has witnessed great developments in the artificially engineered material metamaterial, which has attracted extensive interests due to its unique electromagnetic properties [1]. It is desirable to actively control the EIT effect after the structures are fabricated Various techniques such as thermal tuning, optical control, and micro-electromechanical (MEMS) systems have been employed to achieve the dynamic manipulation of the EIT metamaterials [15,16,17]. In the past few years, a series of graphene-based metamaterial designs have been investigated to achieve the dynamic control of the EIT effect, exhibiting potential applications in controllable buffers and optical modulators [20,21,22,23,24]. Despite extensive studies on the dynamic response of the graphene-based structure, the deformation of the EIT window in the modulating process has not been fully investigated. The tunable slow light performance requires small values and slight changes in the Fermi energy of graphene, which provide more feasibility in practical operation

Geometric Structure and Graphene Model

Results and Discussions

ItFermi can beenergy seen that as the the

Transmission spectra of of the the hybrid hybrid metamaterial with different

Conclusions