Localized Surface Plasmon Resonance Characteristics Of Noble Metal Nanostructures

Localized surface plasmons (LSP) is a kind of electromagnetic mode caused by the interaction between the free charges on the metal surface and the incident electromagnetic wave, and the oscillation is limited on the surface of the structure. The resonance frequent of the LSP is closely related to the metal nanoparticles' shape, size, material and the surrounding environment et al. The localized surface plasmon resonance(LSPR) of metal nanoparticals shows strong electric field effect in the particular wavelength, making many optical effects become more significant, so the LSPR of metal nanoparticals can be widely used in many important fields, such as the Surface Raman Scattering Enhanced, nonlinear optical conversion and biomedical et al. With the development of theory and fabrication technology of the LSP, the design of various nanostructures becomes a research hot topic.In the paper, the finite element method is applied to research the LSP properties of the coupled nanorods arrays, the half-ring/rectangle arrays and the double dolmen arrays. The details of the studies as following:(1) We investigated the transmission property of the arrays of coupled nanorods and studied the influence of the parameters and the surrounding medium on the transmission properties. The results show that the plasmon resonant peaks in the transmission spectra are caused by the localized surface plasmon resonance and electric field couplings of Au nanorods. Hence, the position and intensity of resonant peaks can be tuned by changing the separations between nanorods.(2) We investigated the transmission property of the arrays of metallic half-ring/rectangle and studied the influence of the electric field polarization direction, parameters and the surrounding environment on the transmission property. The research show that Fano resonance appeared when the electric field polarization along x or y direction in the transmission spectra, which caused by the electric field couplings between the half-ring and rectangle. In addition, the Fano resonant peaks are dependent strongly on the structural parameters and the relative position of the half-ring and rectangle, and Fano resonant peaks are also sensitive to refraction index around the arrays of metallic half-ring/rectangle and the figure of merit (FOM) of the resonant modes can be achieve 24.87.(3) We investigated the transmission property of the double dolmen arrays and studied the influence of the parameters and surrounding medium on the transmission property. The results show that the double Fano resonances can be achieved in the dolmen arrays. The double Fano resonances can be separately manipulated by adjusting the coupling gap of the double dolmen nanostuctures. The double Fano resonances are also sensitive to refraction index around the arrays of double dolmen, the FOM can be achieve 26.15.