Study On The Surface Plasmon Resonance Characteristics Of Noble Metal Nano-array Structures

Noble metal nanostructures, which support surface plasmons (SPs), have the ability to manipulate light due to their unusual optical properties. The optical properties of these metal nanostructures sensitively depend on their morphology, spatial arrangements, surrounding medium and direction & polarization state of incident light. The interaction between the incident light and coupled nanostructures produces hybridized collective plasmon modes, and Fano resonances (FRs) can be achieved by the coherent interference of superradiant (bright) mode and subradiant (dark) mode. Due to the interference between different plasmon modes of coupled nanostructures, some interesting phenomena can be observed, such as the generation of high-order magnetic modes and second harmonic. Therefore, metal nanostructures have many important applications in various fields including surface-enhanced spectroscopy, photovoltaic devices, biosensing, optical waveguiding and Fano interferometer.Taking the fact that most of the current researches focus on the single nanostructure, while periodic nanoarrays with certain lattice arrangements have received more and more attention due to their practical value. In this paper, we focus on the optical properties of 2D and 3D noble metal nanoarrays which are excited by linearly polarized light and circularly polarized light.This thesis is divided into three related parts.First part of this thesis respectively introduces three popular calculation methods: finite element method (FEM), finite difference time domain (FDTD) method and discrete dipole approximation (DDA) method. But we focus on discussing the FEM and corresponding simulation software COMSOL Multiphysics in setting boundary conditions and dividing meshes..In the second part, different ways of manipulating surface plasmon resonances are shown, which including changing the morphology & spatial arrangement of the nanostructure, altering the surrounding medium and controlling the direction & polarization state of incident light. Moreover, the circular dichroism properties of 3D metal-dielectric-metal nanoarrays is studied and the fluorescence enhancement induced by surface plasmon resonance is considered.In the third part of the paper, a periodic nanorings with built-in V-shaped nanowedges (NRBV) are investigated theoretically. Tunable ultrahigh order Fano resonances are achieved and they are found to be sensitive to geometric parameters and surrounding dielectric environment of the planar nanostructure. High order Fano resonances can be suppressed or enhanced by adjusting the opening angle of the nanowedge, the size of the nanoring and the aspect ratio of the nanowedge. Moreover, manipulating the offset of the built-in nanowedge, or filling dielectrics asymmetrically can revive suppressed Fano resonances. Meanwhile, stronger plasmon resonances emerge alternately in the two parts of this planar nanostructure. This periodic plasmonic nanostructure produces ultrahigh order plasmon resonances and stronger electric field enhancement, which have great potential applications in multi-wavelength surface enhanced spectroscopy and biochemical sensing.