Research On Electromagnetically Induced Transparency Mechanism And Application Based On Graphene

Electromagnetically induced transparency(EIT)is a coherent nonlinear optical effect that produces a narrow spectral window of transmission near an absorption line.The transparency windows with high transmittance and strong dispersion have great application prospects,including sensing,slow light control,modulation and so on.However,traditional EIT implementation is subject to strict experimental conditions,such as stable gas lasers and low temperature environments.In order to overcome strict experimental conditions,the EIT-like phenomenon based on metamaterial structure has been extensively studied.As a novel two-dimensional material,graphene has become a hot spot in the field of EIT metamaterials with its good dynamic conductivity.This paper studies the EIT effect and physical mechanism model of the atomic system;studies and deduces the basic physical properties and characterization modeling methods of graphene;designs and analyzes three graphene EIT metamaterials,and discusses their properties and applications.The main work results are as follows:Firstly,the EIT effect caused by the strong coupling between the dipole resonance of the nano-disk and the quadrupole resonance of the nano-ribbons is proposed.The fermi energy is adjusted by the ion gel to achieve active control of the transparency window.It can be used in mid-infrared refractive index sensing with a sensitivity of 3016.7nm / RIU and a quality factor higher than 12.0.Then,we propose the EIT effect of strong coupling between two orthogonal graphene T-type resonators.Actually,T-type resonator is composed of a dipole resonance strip and a conductive strip.The Fermi energy can be easily adjusted through the conductive strip,reducing the influence of the ion gel strip on the sensing sensitivity,effectively improving the sensing performance,achieving a sensitivity of4960nm/RIU and a quality factor higher than 11.4.And due to the particularity of its structure,polarization is insensitive to horizontal and vertical polarization.Finally,the EIT effect caused by the bright mode coupling between the dipole metal strip and the quadrupole U-shaped metal ring laid on the polyimide layer is proposed.The two-dimensional graphene surface,non-dispersive medium and substrate are integrated under the polyimide layer,and the EIT effect is actively controlled by changing the voltage between the graphene surface and the substrate silicon.This structure can be used for terahertz modulation with a maximum modulation depth of 83.4%.In addition,its slow light characteristics are analyzed,and the light in the transparency window will experience a positive group delay of up to 8 ps.