Enhanced Third Harmonic Generation With One-dimensional Nobel Metallic Nanoparticle Arrays

The local surface plasmon resonance of noble metal nanostructures can effectively limit the incident field energy around the structure,which is of great significance for enhancing the interaction between the light field and matter at the nanoscale.Among them,nonlinear effects based on noble metal nanostructures(such as third harmonic generation)have been widely used to achieve ultrafast nonlinear sodium photonic devices.However,in general,localized surface plasmon resonance has a strong radiation loss,which will weaken the nonlinear effects based on noble metal nanostructures.In order to solve this problem,an array structure composed of noble metal nanoparticles can be used,in which local surface plasmon resonance is coupled with array Rayleigh anomaly to generate surface lattice resonance,thereby effectively suppressing the radiation loss of the system while the incident field energy can be well confined to the array,and its resonance quality factor can be improved by more than an order of magnitude.Therefore,the surface lattice resonance can effectively enhance the nonlinear response represented by the third harmonic generation.However,in order to generate surface lattice resonance,it is necessary to prepare a regularly arranged array structure,which places high demands on micro-nano processing technology.At present,the top-down etching technique can effectively prepare such a regular array structure,but it has the problems of high cost and limited sample size.In this paper,a method for generating surface lattice resonance using a one-dimensional noble metal nanoparticle array is proposed.This array structure can be prepared in a large area by using a "bottom-up" self-assembly technique,thereby effectively reducing the cost.The paper focuses on the third harmonic generation emission characteristics based on the surface lattice resonance of the above-mentioned one-dimensional noble metal nano-array structure.The effects of different spacing and single-chain arrangement on the optical response of the chain structure are discussed.The effects of local surface plasmon resonance and surface lattice resonance on the enhancement of the third harmonic generation effect are also studied.Main work includes:(1)Study of the local surface plasmon resonance phenomenon of gold nanosphere particles in one-dimensional single-chain arrangement,analyze of the resonance near-field distribution characteristics under the above conditions,and discuss one-dimensional precious metal nanoparticles.The localized surface plasmon resonance characteristics of the localized surface plasmon resonance under different nanoparticle numbers were compared.The local resonance characteristics generated by polarized light incident in different directions were compared.The spacing between the nanoparticles and the surrounding environment were also studied.The effect of the rate on local resonance.Based on the above results,the paper further designed a one-dimensional noble metal nanoparticle array structure,and studied and calculated the modulation effect of array period and incident polarization direction on the lattice resonance of the array surface.The results show that a stronger surface lattice resonance can be produced when the polarization direction of the incident light is parallel to the longitudinal direction of the one-dimensional noble metal nanoparticles.Therefore,it is expected to achieve effective modulation of the third harmonic emission characteristics of the array structure by adjusting the polarization direction of the incident light,the pitch of the nanoparticles,the period of the array,and the arrangement of the single-chain.(2)Study of the enhancement characteristics of the surface lattice resonance of the one-dimensional gold nanosphere array on the third harmonic generation emission.This part focuses on the influence of the period of the one-dimensional gold nanosphere array,the polarization direction of the incident field,the refractive index of the surrounding medium and the incident field wavelength on the third harmonic generation emission intensity of the structure.The results show that when the incident field is lattice-resonantly matched to the array surface,a stronger third harmonic generation emission can be produced.In addition,the surface lattice resonance of the one-dimensional gold nanosphere array can effectively adjust its third harmonic emission characteristics.These results have important reference value for the design of ultrafast nonlinear micro/nano photonic devices.