Gold And Silver Nanoparticles Of Femtosecond Laser Technology And Nonlinear Optics Research

Metal nanoparticles show surface plasmon resonance under the excitation of thelight. The effect can lead to the enhancement of local field, which makes that the metalnanoparticles exhibit large optical nonlinearity and ultrafast response. The materialswith large optical nonlinearity and ultrafast response are the key to the preparation ofultrafast optoelectronic devices. The research of optical nonlinearity of metalnanoparticles helps us to understand the process of energy transfer between the electronand electron, electron and phonon, phonon and phonon, and helps us to clarify theorigin of optical nonlinearity. The surface plasmon resonance peak of gold and silvernanoparticles is in the visible range, which attracts attention of scientists. In this thesisthe optical nonlinearity of gold and silver nanoparticles is investigated.Firstly, gold and silver nanoparticles are prepared by using femtosecond laserablation and the dynamics of ablation process is described. Optical nonlinear absorptionof gold and silver nanoparticles is reserched at different repetition rate. and differentenergy by using femtosecond laser open Z-scan technology. We found that goldnanoparticles show the reverse saturable absorption in the wavelength of400nm. While,silver nanoparticles show a saturable absorption at low energy, and shows thetransformation from saturable absorption to reverse saturable absorption. Furthermore,we found that the symmetry of experimental curve is affected by repetition rate. Finaly,the ultrafast dynamic process of gold and silver nanoparticles is researched by usingfemtosecond laser pump-probe technology. The characteristic relaxation time of goldand silver nanoparticles is obtained by fitting the curves.