Theoretical Study On Tunable Graphene Terahertz Metamaterials

Electromagnetic induced transparency was first found in quantum systems.The principle of EIT is that the quantum interference occurs so that electromagnetic waves that should be absorbed by the material can be transmitted through the material.This phenomenon has a broad application prospect,but due to the harsh implementation conditions,the existing technical level cannot support,the practical application of electromagnetic induced transparency is limited.However,eit-like phenomena in terahertz metamaterials are easy to realize,which greatly improves their application value.In metamaterials,each resonant element is prepared into a periodic element structure,which can achieve electromagnetic induced transparency.However,once the periodic structural elements in the existing metamaterials are fixed,the transparent window of EIT is fixed accordingly,and its transmission characteristics cannot be dynamically tuned,which limits its application scope.In this paper,two kinds of tunable terahertz metamaterials based on graphene are proposed to solve the problems of difficult EIT tuning modes and insufficient tuning depth at home and abroad.The main work is as follows:1.A graphene-based tuned terahertz EIT metamaterial is designed.The structural unit consists of two graphene strips perpendicular to each other in a T-shape.By changing the structure of graphene and applying voltage to both ends of the metamaterial,the simulation results show that the structure is light-dark coupling.When the Fermi energy level changes from 0.1e V to 0.3e V,the electromagnetically induced transparent peak can be modulated within the range of 0.32 to 0.47 THz,with a modulation depth of 32%,and the modulation range and depth can be further improved by further increasing the Fermi energy level.When simulated with external voltage,Fermi energy level changes from 0.2ev to 0.3ev at 0.47 THz,and the transmitted value can be switched between 0.114 and 0.957,with a modulation depth of 88.1%.2.A graphene-based dual-band electromagnetic induced reflection metamaterial is designed.The structure consists of two horizontal graphene strips and a vertical hollow strip,with metal electrodes at each end for applied voltage.According to the two-particle coupling model and the extended three-particle coupling model,the simulation results show that transparent peaks appear at two different frequency bands(0.859 THz and 0.935THz)in the reflection curve,indicating that metamaterials are coupled in a dark-light-dark mode.By simulating the horizontal strips of graphene on both sides,the modulation depth of the two transparent peaks that appear separately can reach 46.31% and 46%,respectively.At the same time,doping was conducted to different degrees on both sides of graphene.When the Fermi energy level of graphene on both sides was 0.6e V and 1e V,two transparent peaks appeared at the same time,and the amplitude modulation depth reached 39.06% and 39.06%,respectively.By calculating and fitting the three-particle coupling model,the calculated results are close to the simulation results,which proves that the simulation results are accurate.