Study Of Femtosecond Laser Induced Nanoparticle Formation

Nanoparticle has great research and application value in many areas because of its unique shape and performances.The method of femtosecond laser produced nanoparticles holds the stable,rapid,and controllable features,and already becomes one of the advanced technique for nanoparticle formation.And laser induced forward transfer can be used for producing nanoparticles on substrate by transfer micro materials from metal thin films.In this thesis,large area and high efficiency nanoparticle formation is studied with experimental and theory analysis,by using high repetition rate fiber femtosecond laser system.The works of the thesis are summarized as follows:1,50 MHz high repetition fiber femtosecond laser is used to induce nanoparticle formation from copper thin films.Laser induced forward transfer is applied in the experiments.While comparing the results of dot processing and line scanning,the influenced of laser power,scanning interval is discussed.Appropriate parameter is obtained based on the previous study.This research results plays a guide role for later study of high repetition femtosecond laser nanoparticle producing.2,On the basis of experimental and theoretical experience accumulated from 50 MHz study,500 KHz femtosecond laser is used as the laser source for laser induced nanostructure thin films formation.Metal films composed of different nanostructures can be obtained by changing the parameters of femtosecond laser source.Firstly,nanoclusters are produced under lower power,and their sizes grow bigger with the power increasing;then nanowires appear when the power rises to a certain level.Based on the experiment results,some dynamic processes of the interaction between femtosecond laser and materials are discussed.On the basis of the mechanisms,copper thin films with three different thicknesses,which are 20 nm,40nm and 200 nm,are studied in the same experimental conditions.According to the results,appropriate parameters are proposed for nanoclusters and nanowires.The mechanism of femtosecond laser and material interact is discussed,and a new method is provided for mass production of nanostructures.