Studies Of Toroidal Resonance In Graphene Metamaterials

Metamaterials,are complex deep-wavelength structures that produce responses derived from super-atom and electromagnetic field radiation.Unlike natural materials,the behavior of metamaterials depends on their size,shape and structural design,rather than chemical composition.Outstanding features,such as slow light effects,negative refractive index,invisibility cloaks,and sensing,have all been reported using metamaterials.This paper mainly studies the three-layer graphene metamaterial,such as the resonant mode of the surface plasmon — — toroidal dipolar mode.The main chapters of this paper are arranged as follows:The first chapter briefly introduces the concept of metamaterials,the theory of equivalent media,development status and prospects,and focuses on the concepts,characteristics such as photonic crystal,negative refraction phenomenon,slow light effect.In chapter 2,we introduce the surface plasmon on graphene surface,and analyze the structural parameters,Fermi levels and tunability of graphene to generate tunable electromagnetic characteristics in terahertz band,such as multi-band electromagnetic induced transparency and graphene EIT system based on coupling mode theory.We also introduce the similarities and differences between the Fano resonance and the toroidal dipole resonance.Under the same conditions,the Q value of the toroidal dipole is larger.The third chapter introduces the theoretical basis and calculation methods,firstly dispersion theory: Drude model and Lorentz model;Secondly,electromagnetic field numerical analysis methods: finite element method and finite difference time domain method;electromagnetic simulation software: CST Microwave Studio and HFSS.The fourth chapter studies the concept of graphene-basedmagnetic vortex resonance and electromagnetic response of resonance coupling mode,and to explore the characteristics of these coupling,in-depth study of electromagnetic effects in graphene sandwich metamaterials and analyze the underlying mechanism,characteristics and application of some special optical phenomenon,and by adjusting the excitation conditions of metamaterials,we also study the tunable responses under different incident angles and polarizations.The fifth chapter summarizes and prospects this thesis.