The Harmonic Enhancement Of Nonlinear Medium By Plasmon Resonance

With the development of nanofabrication and preparation technology,plasmon resonance optical property of metal nanoparticles has been widely studied and applied in many fields,such as nonlinear optics.Due to the higher local field enhancement effect of this property,which has important application prospects in the field of nonlinear medium,such as harmonic enhancement,two-photon luminescence enhancement and Surface-Enhanced Raman Scattering(SERS).In this thesis,based on the localized surface plasmon resonance(LSPR)characteristic of Au Nanorods(Au NRs),we use the Finite Difference Time Domain(FDTD)method to do the simulation research.We simulated the localized surface plasmon resonance properties of Au NRs with different structures,environments and the enhancement of second harmonic generation of nonlinear medium,after analyzed the result we obtained the optimal Au NRs structure with field enhancement and matching conditions.When the aspect ratio of the Au NRs is 4.0:1,the nonlinear medium of nested Au NRs array has a high conversion efficiency of second harmonic generation,that signals intensity of SHG is nearly 3.22 times than that of the nonlinear medium.Based on the simulation results,the optimal size structure of Au NRs were prepared,the Au NRs are embedded in nonlinear materials with two order nonlinear polarizability(CdSe),under the action of femtosecond laser,the experimental results show that signals intensity of second harmonic generation of nonlinear materials embedded Au NRs is nearly 3 times as much as that of the nonlinear materials.In order to further increase the intensity of local electromagnetic field of metal nanoparticles,LSPR peaks are tuned in the near infrared wavelength region at the same time,we use the coupling effect of Au NRs assembly to achieve local field enhancement of nearly 5 times,the results showed that enhancement effect of second harmonic generation of Au NRs assembly is better than that of single Au nanorod in nonlinear medium.