Surface Plasmons And Nonlinear Optical Properties In Bimetallic Core-shell Nanoparticles

Surface plasmon resonances and nonlinear optical properties in bimetallic nanoparticles are researched in this thesis. With the aid of the theoretical formulas and numerical simulations, it has been proved that the plasmon resonances frequency and nonlinear optical properties can be enhanced by tuning the physical properties, structural parameter and the volume fraction of coated particles. and so on,the theoretical instructions will be provided for the composites with the enhanced nonlinear properties. Our main work is as follows:In Chapter 1, a general literature review is made on the surface plasmon resonances and nonlinear optical properties in bimetallic nanoparticles, and then our main work is simply presented.In Chapter 2, we mainly study the multipolar plasmon resonante properties of spherical nanoparticles of the bimetallic shell structure in the electric field of point charge. The research shows that the frequency of plasmon resonances and the decay rate correspond to different polarized modes and also vary differently with the increase of the shell thickness. In addition, we also discuss the far field effect of Gold/silver nanoshell structures. We find the asymmetrical Fano resonance of scattering cross section. And we can change the plasmon resonances on the surface of coated particles by tuning shell thickness, so the asymmetrical degree of Fano resonance can be adjusted.In Chapter 3, we mainly make our researches on the nonlinear optical properties of composite material with Gold/silver and Silver/gold core-shell nanoparticles. The research shows that third order nonlinear polarizability can be enhanced by varying the core-shell structure, structural parameter and volume fraction of the particles. It also shows that there exists an optimal structural parameter, so the maximal figure of merit (FOM) in the composite materials can be found.In Chapter 4, the main idea of this thesis is summarized and the results of the study will offer a reference for further study in this field.