Research On Tunable Terahertz Electromagnetic Induced Transparency Based On Graphene Metamaterial

Electromagnetic Induced Transparency(EIT)caused by metamaterial in the THz wave band is a kind of electromagnetic phenomenon formed by the artificial periodic unit structure.It has a typical transparent window in the frequency spectrum of THz transmission which is of great significance in the period of slow light,Optical storage and optical sensing.However,the fixed shape and size of the periodic structure element make the transparent window of the EIT relatively fixed and can't be dynamically modulated,which greatly limits the realization of the device function.To solve the problem of some of the tunable EIT is not easy to achieve and the characteristics of insufficient depth of modulation at home and abroad,in this paper,two kinds of graphene-based tunable EIT metamaterial structure are proposed based on the properties of graphene with different conductivity under different applied bias voltage.The main research works are as follows:1.A gold-graphene cross EIT metamaterial structure is proposed,which is composed of an internal golden ring structure and an external closed graphene ring structure.In order to analyze the formation mechanism of EIT,the resonant characteristics of the golden structure and the graphene structure were studied by numerical simulation software.The surface currents of the EIT resonant valley and the transparent peak were monitored.The simulation results showed that the structure had bright-dark mode coupling characteristics.The metal-graphene structure exhibits different EIT response characteristics when changing the Fermi Energy of graphene.The tunable characteristics of the EIT are analyzed.The modulation depth of the transparent window and the size of the corresponding group delay are calculated.The results show that the structure can realize amplitude modulation and slow lightmodulation.2.In order to obtain the dynamic modulation of the transparent peak at the EIT fixed frequency and the greater modulation depth,a graphene-graphene metamaterial structure is proposed,which consists of the left graphene short strip and the right double closed graphene ring.The relative distance between the left and right graphene was optimized by numerical simulation software.The formation mechanism of EIT was analyzed and the coupling characteristics of the structure were proved.And the graphene-graphene structure exhibits different EIT response characteristics while changing the Fermi level of graphene structures on the left and right sides.The tunable characteristics of EIT transmission and absorption are analyzed,and the modulation depth and the group delay of the structure are calculated.The calculation results show that the structure can realize the amplitude modulation and slow modulation of the transparent peak at fixed frequency,and have a larger modulation depth.3.A two-coupled-particle model is proposed and fitted with the simulated EIT curve.The fitting curve is well matched with the numerical simulation curve.The fitting results show that the two-particle coupling model and the coupled model theory are accurate.