Research On Plasmon Induced Transparency Based On Graphene Metamaterials

Metamaterials are kinds of periodic composite materials with artificial design structure and extraordinary physical properties that natural materials do not have.Since the scale of the metamaterials is smaller than the wavelength acting on it,it is possible to exert an influence on the wave.Therefore,it is possible to break through the limitations of certain natural laws by orderly structural design of key physical dimensions of materials,thereby achieving extraordinary physical characteristics.Graphene is a honeycomb-arranged two-dimensional carbon atom plane with a single atomic thickness.Graphene has a metallic surface on the surface in the terahertz and near-infrared bands,which can generate surface plasmons.The Fermi energy of graphene can be well adjusted through chemical doping or electrostatic control,thereby changing the surface conductivity.In addition,compared with plasmon-induced transparent structures composed of noble metals,graphene has relatively low loss and strong light confinement characteristics,so the metamaterial structure composed of graphene is designed to tunable plasmon-induced transparency.In this paper,we use finite element method to theoretically design and study two different types of graphene metamaterials that can achieve plasmon-induced transparency.The research results are as follows:1.A graphene-based metamaterial for THz plasmon induced transparency(PIT)is presented and numerically studied in this paper,which consists of two horizontal graphene strips attached to continuous vertical wire separately.The calculated surface current distributions demonstrate that the distinct PIT window results from the near-field coupling of two bright modes.To explore the physical mechanism of PIT effect,we employ the coupled Lorentz oscillator model.The transmission spectra obtained with this model fit well with the simulation results.The performance of the PIT system can be controlled through the geometry parameters of graphene strips.Moreover,the transparency window can be dynamically tuned by varying the Fermi energy and the carrier mobility of the graphene strips.Slow light effect is alsoexplored in our proposed structure and it can achieve 1.25 ps when Fermi energy is1.3 eV.Finally,the position of the transmission window with the variation of the nearby medium refractive index is examined.2.A distinct transparent window is realized in a novel design of plasmon-induced transparency(PIT)THz metamaterial,consisting of two identical graphene strips and a cross-shaped resonator in right middle,namely,a |+| model.The two strips serve as the dark resonator and the crossed graphene plays the bright mode.Active control of the transmission peak can be modulated from the on-state to the off-state only by breaking structure symmetry.Furthermore,the transparent window can be dynamically adjusted by changing Fermi energy in a non-contact way.More importantly,the proposed PIT structure achieves a maximum group delay of 13.28 ps,which is much higher than that in the previous paper.The position of the transmission window can be adjusted by varying the nearby medium,and this property can be used(but not limited to)in a sensing application.