Control Of Metamaterials Electromagnetically Induced Transparency Based On Graphene

Metamaterials are artificial engineered subwavelength structures,and show many novel optical phenomena such as negative refraction,super-resolution,optical cloaking and Electromagnetically Induced Transparency(EIT)-like effect,etc.Particularly,EIT-like phenomenon is an optical analogy which is original from quantum coherent effect.In terms of EIT phenomenon,it receives widespread attention for slow light,strong nonlinear optics and the applications of lasing without inversion.Compared with EIT phenomena,EIT-like phenomena controlled by metamaterials have advantages for changeable structure.With futher study of this phenomenon,we not only innovate the scientific theory of the interaction between light and material,but also explore its rich potential applications.So far the position of transparency peak and group velocity have been tuned by varying the parameters of structures.The study of passive adjustment is quite clear for realizing slow light effect.The directions that peoples consider are active tuning in the next step.Transparency window and its resonance peak are tuned according to requirements.In this thesis,active tuning of metamaterials EIT transparency window and slow light effect can be realized by the inductive coupling between graphene and metamaterials.which is based on graphene/metamaterial hybrid structures.This thesis focuses on the control of metamaterials EIT phenomenon and is based on graphene from theories and simulations.The main work of this thesis includes:1,we use perturbation theory to study the influence of peak position by the coupling of graphene and metal structure.The result is that spectral shift of the resonant frequencies is proportional to the imaginary part of graphene's surface conductivity.We derivate the transmission formula from the coupled mode theory.2,we study the change of metamaterials EIT peak and group velocity by varying separation between a radiative element and a dark element or the fermi energy of graphene.We find that when the separation is 30 nm,the groupvelocity can be reduced to 2.862% c without graphene.With the changing of graphene's fermi energy,the resonance peak can be blue shifted or red shifted and the group velocity can be tuned.3,modulation of EIT phenomenon can realize an active tuning of peak position and group velocity by using graphene with different fermi energy.Finally,we use the formula to fit the transmission of EIT,and make sure what the role of structure parameters and graphene do in metamaterial EIT phenomena.We find the dark mode play a major role in EIT phenomena by separating modulation of bright mode or dark mode.