Research On Metamaterials Based Electromagnetically Induced Transparency Effect And Absorber Device

Terahertz waves(Terahertz,THz)possess many special properties that are different from other electromagnetic waves,which have attracted extensive attention and research from many researchers and have made rapid progress in a wide range of fields such as information and communications technology,biomedicine,safety inspection.However,the lack of terahertz band electromagnetic materials has greatly limited the development of terahertz technology.Metamaterials have unique electromagnetic characteristics in the terahertz band,which has provided strong support for research on terahertz devices.This thesis focuses on the characteristics of graphene-based metamaterials electromagnetically induced transparency(EIT)effect and Dirac semimetal films(DSF)based metamaterials absorbers.The main research content of this thesis is as follows:1.A dynamically tuned metamaterial structure device with electromagnetically induced transparency effect was studied.The top layer of the device consisted of a graphene ring resonator(RR)and a pair of graphene nanorods.Using the bright and dark mode coupling method,and the bright mode coupled to the excitation field produces a magnetic field that is ultimately coupled to the dark mode.The electromagnetically induced transparency optical phenomenon was finally achieved.The coupling strength can be adjusted by the degree of asymmetry and the distance between the bright and dark modes.Then,Babinet's principle is applied to transform the EIT structure into an electronically induced absorption(EIA)structure.In addition,the use of graphene has the gate-voltage-dependent characteristics;thus,we may dynamically tune the resonant frequency of the transparency/absorption window by changing the Fermi energy of graphene without re-optimizing and re-fabricating the structure.2.A three-dimensional Dirac semimetal films based tunable metamaterial absorber was studied.The Dirac semimetals films based tunable single-peak absorber and dual-band and broadband absorbers were studied respectively.The results show that the resonant frequency of the absorption peak and the reflection valley of the single-peak absorber shifts toward high frequencies with the increase of the Fermi level of DSF.And perfect absorption of electromagnetic waves is achieved.Using the idea of superimposing the extended peaks with absorption peaks,by combining two square-shaped-resonator of single-peak absorbers in one unit cell with different sizes,dual-band and broadband absorption is realized.And by changing the Fermi level of the DSF layer,dynamic tuning of the absorption resonance of the dual-band and broadband absorbers in the terahertz band can be achieved.