Study On Tunable Electromagnetic Induced Transparency Devices Based On Metamaterials

Metamaterials are synthetic composites with extraordinary physical properties.Compared with natural materials,it has very unique physical properties.In recent years,researchers have conducted in-depth research on metamaterials.Novel terahertz devices based on metamaterials such as absorber,polarizer,sensor and so on have emerged.In particular,the phenomenon of electromagnetically induced transparency(EIT)based on metamaterials has attracted widespread attention.The slow light characteristic of this phenomenon greatly promotes the development of terahertz switches and modulators.With the study of electromagnetically induced transparency,tuning the EIT effect and actively controlling the transmission window has become a hot topic in the research field.In this thesis,we study the electromagnetically induced transparency effect based on graphene and Dirac semimetal.The main contents and conclusions of this thesis are as follows:1.An electromagnetically induced transparency structure device based on bright-bright mode coupling of graphene is studied.The upper layer of the device structure is composed of graphene nanorods and graphene semirings,and the lower layer is a dielectric substrate.The results show that both nanorods and semirings in graphene layer can be excited by incident light,showing two resonance modes.When placing these on the dielectric substrate at the same time,the phenomenon of electromagnetic induced transparency occurs due to weak hybridization between the two bright mode.The influence of distance L between graphene nanorods and graphene semirings and the inner diameter R1 of graphene semirings on EIT effect was studied.Based on the gate-voltage-dependent characteristics of graphene,the tunability of EIT spectra at different Fermi energy is studied,and the group delay at different Fermi energy is also obtained.By adjusting the Fermi energy of graphene,the group delay is close to 0.4 ps.2.An electromagnetically induced transparency structure device based on bright-bright mode coupling of Dirac semimetal is studied.The upper layer of the device structure is composed of left and right parts of Dirac semimetal,the middle layer is composed of silicon dioxide,and the bottom layer is composed of silicon.The EIT tuning theory of bright-bright mode is validated by analyzing the electric field and surface current.The influence of the relative distance between the left and right parts of Dirac semimetal structure and the thickness of Dirac semimetal layer on the EIT window are also studied.Due to the tunability of Dirac semimetal’s conductivity,the structure exhibits different EIT response characteristics when changing the Fermi energy of Dirac semimetal structures on the left and right sides.Thus,the dynamic tunable of the group delay at the transmission peak can be achieved without optimize the geometry and re-manufacture the structure.