Research On Tunable Electromagnetic Properties Of Terahertz Metamaterial Based On Graphene

Terahertz(THz)metamaterial has an increasingly important position with the rapid development of information technology,which is of great significance for the realization of optical storage,modulator,slow light and light sensing.However,due to the fixed shape and physical size of the periodic THz metamaterial,the dynamic modulation of the transmission can’t be achieved,which greatly restricts the realization and practical application of the devices.In this paper,three graphene-based tunable metamaterial structures are proposed based on the fact that graphene conductivity can be flexibly tuned by electrostatically doping,which achieve perfectly dynamically tunable of THz metamaterial.The main research works are as follows:An asymmetrically double T-shape graphene-based THz metamaterial structure is proposed,which can enable tunable electromagnetic properties of double EIT windows.The tunable characteristics of corresponding structures are studied by electromagnetic field numerical simulation software.On the basis of above,the two-oscillator EIT model was used to research the electromagnetic properties,which verified the correctness of the coupled mode theory.In addition,by changing the Fermi level of graphene,the dynamic modulation of single asymmetric T-shape and asymmetrically double T-shape graphene-based metamaterial structure have been achieved.The results show that the structure has great potential application in the field of multi-band slow optical devices and vision sensors.An orthogonally twisted split ring resonators(SRRs)graphene-based THz metamaterial structure was proposed,in which the separate vertical SRR alone was view as the bright mode and the separate horizontal SRR was view as the dark mode.Due to the damaging interference caused by the near-field coupling of the light and dark modes,the electromagnetic induced transparent window(EIT)was induced.To verify the rationality of the designed structure,the electromagnetic field numerical simulation software was used to monitor the surface current and electric field at the corresponding resonant valley and transparent peak,which explained the formation mechanism of EIT and proved that the corresponding of the structure met the bight-dark mode coupling.On the basis of above,by changing the Fermi level or the relaxation time of graphene,not only the dynamic tuning in a certain frequency range but also the dynamic tuning of the amplitude of the EIT transparent peak at a fixed frequency is achieved.Based on the previous work,a T-shape and orthogonally twisted split ring resonators graphene-based complementary THz metamaterial structure was proposed.More electromagnetic induced transparent windows can be achieved by near-field coupling between the different structures.The surface current at the resonant valley and the transparent peak was monitored by electromagnetic field numerical simulation software.On the basis of above,by changing the Fermi level of graphene,THz metamaterial exhibits different EIT response characteristics,that is to say,it achieves dynamic tuning within a certain frequency range.