Research On Silver Nanodimer Plasmon Coupling And Plasmon Waveguide Coupling

In this thesis,we mainly study the coupling of plasmons in the dimer composed of a metal nanoring and a metal nanorod,and the coupling between surface plasmon waveguides constructed with rectangular cavities.The coupling process of plasmons can achieve the strong effect of field in the dimer of metal nanoparticles,which is very important for trapping single molecules and realizing the surface-enhanced Raman scattering and other effects.It can be seen that dimer is the basic unit to study the coupling effect of plasmon.The main work of this thesis is as follows:1.Plasmons coupling and anti-crossing of the asymmetric dime.The plasmons coupling of an asymmetric dimer consisting of a metal nanoring and a metal nanorod is studied.Under the action of light field,the metal nanoring in the dimer always produces a bright mode regardless of the polarization direction of the light field due to its own symmetry.However,when the metal nanorod is perpendicular to the polarized direction of the light field,the nanorod will be affected by the nanoring and produce a dark mode.The bright mode of the metal nanoring will split into two modes under the influence of the dark mode of metal nanorod;the two splitting modes show an asymmetric anti-crossing with the increase of the nanorod's length.When the nanorod and the directions of the polarized light have different angles,the longitudinal component of polarized light field in the nanorods will excite the nanorod to produce a bright mode,and at the same time,the nanorods will produce a dark mode under the influence of nanoring;we study the coupling phenomenon of plasmon generated by the dimer for this cases.We propose a new coupled physical quantity ?? in order to give a clear physical explanation to the numerical results,that is the offset of the resonance frequency of the independent oscillator due to the occurrence of coupling.By the harmonic oscillator coupling model and the established plasmon coupling(CPEP)model,it is revealed that the coupling between bright mode and dark mode is a form of coupling under the influence of Coulomb potential and electrostatic potential.The results obtained by this model are in good agreement with the numerical results,and a reasonable physical explanation is given.2.Surface plasmon waveguides couplingThe surface plasmon waveguide coupling is simulated based on the finite element method(FEM)in this thesis.The waveguide structure is composed of an air nano-rectangular cavity and a metallic silver structure.By changing the parameters of the waveguide structures,the plasmon waveguide coupling and transmission spectra splitting are obtained,and the interaction between bright and dark modes is observed.Meanwhile,the mechanism of generating EIT in atomic energy level system under the action of light field is used to explain the waveguide coupling phenomena.The results obtained in this paper are of great significance for the in-depth understanding of the interaction and the principle of the plasmons in the waveguide structure,and have important reference value for its further applications.