Theoretical Study Of The Fano Resonance And Sensing Characteristics Of Au Nano-clusters

With the development of the computer and lithography technology,the typical surface plasmon of metal nanoparticles cluster shows great superiority.Nanostructures will produce high absorption to the photon energy and generate local surface plasmon resonance(LSPR)when the frequency of the incident light matches theirs.In particular,noble metal such as Au and Ag can produce strong LSPR,forming the Fano resonance.Fano resonance can reduce the energy loss and obtain high electric field.The tunability and sensing characteristic related to the Fano resonance also show great potential for applications.This paper designed three different nanoparticles clusters,studied their Fano resonance and applications in sensing,surface enhanced Raman scattering(SERS).The research work consists of the following three parts:1.A heptamer composed of asymmetric split nanorings was designed.We investigated the mechanism of the multiple Fano resonances in the extinction spectrum and analyzed the variations of the resonances with the change of the asymmetric degree of the nanorings.The structural sensitivities to the surface molecule are studied by using the p-mercaptoaniline(pMA)as the detective molecule.We also discussed the robust of the structure itself by shifting the central nanoring to three different directions and to the disturbance of the molecule by using the pMA as the disturbed molecule.These all have important guiding significance to the split clusters.2.The clusters comprising of nanorods or nanospheres can form sharp Fano resonances.We designed a double layer system consisting of two identical single layers of nanorods.More complex Fano resonances occurred due to the interaction of the two layers.The interaction process was deduced by the Hamiltonian.Then we investigated the tunability of the structure by varying the structural parameters.We also studied the influence to the Fano resonance via shifting the bottom layer,which expanded its application in displacement sensing.3.The Fano resonances in the transmission spectrum of a nano-bowtie tetramer were considered in this paper.We investigated the effects of the incident light to the Fano resonances and field enhancement with linear polarization of different degrees,circular polarization and different incident angles.We determined the best radius and incident light parameters used in the following discussion.The influence of the structural asymmetry to the Fano resonance was investigated,as well as the refractive sensitivity of the triangular holes.We also studied the displacement sensitivity of the spectrum to the structural components,which expand the applications of the bowtie tetramer.