Research On The Fano Resonance Phenomenon In Metal Nanostructures

Surface plasmon resonance(SPR)is collective oscillation of charges on the surface of the metallic nanoparticles with the distinct resonance frequencies.The resonance frequencies can be actively affected by the shape of metal nanoparticles,the size and the surroundings.However,surface plasmon polaritions(SPPs)at the metal/dielectric interface decay due to Ohmic losses and losses from surface roughness.Fano resonances with a narrow line width can be produced by using the superradiant bright resonance to excit the subradiant dark resonance,which can reduce the radiation loss.In particular,as the Fano resonance is sharp and sensitive to refractive index changes of the surrounding environment,Fano resonances of the metallic nanoparticles have been remarkably explored in high sensitivity refractive index chemical and biological sensors.In this paper,we designed some kinds of metallic nanostructures that can achieve Fano resonances and studied generated theory including related characteristics with analyzing the absorption and scattering spectra.Now we show our key works as follow:1.We mainly introduce the research background and the recent development of surface plasmon polaritons(SPPs);and the basic properties of the SPPs are briefly introduced.2.The basic concepts and research status of surface plasmon resonance and Fano resonances are introduced;and we briefly introduce the Finite Element Method(FEM)used in it.3.The nanostructure consisting of two rings with different radius is simulated by using simulation software,analyzing the scattering spectra,the distribution of charge;we propose a ring-shaped “hexamer” cluster consisting of six nanorings for Fano resonance generation in near-infrared regions.The generation principle of Fano resonance and its possible application are analyzed by its absorption spectra,the scattering spectra and charge distribution.And by controling the parameters of the designed hexamers,the Fano line width(FLW)can be narrowed to 0.028 e V with contrast ratio(CR)of 86 %.4.We simulate the scattering spectra of plasmonic Fano resonances in heterogeneous nanostructure consisting of a rod and concentric square ring-disk.Compared with the nanostructure of the same material,twinned asymmetric Fano-like dip are obtained in the heterogeneous nanostructure and the effective mode volume can be reduce to the minimum 4.3 × 10-238)3 and 8.8 × 10-238)3 respectively which is an order of magnitude smaller than that of the same material.