Dynamic Processes Of Bubbles Generated By Femtosecond Laser Filamentation In Water

Recently,with the rapid development of the intense optics,the femtosecond laser has been widely applied in many research areas.Filamentation transmit in media,especially when plasma is present,many nonlinear phenomena are generated,such as photoionization,supercontinuum generation,terahertz radiation and so on.Therefore,the study of femtosecond laser pulse transmission characteristics in media has attracted great interest of researchers,and has become a hot research direction nowadays.In this paper,bubbles are generated when the filamentation in water is studied.Firstly,the development of laser technology and the physical mechanism of the filamentation in media are reviewed in this paper.Then,the main physical processes of filamentation in liquid media are described,the changes of physical and chemical properties associated with filamentation are introduced,and several methods for the determination of filamentation are briefly introduced.In the experiment,the dynamics of bubbles induced by femtosecond filament is monitored by a CCD coupled with a microscope.We mainly focus on the size and rising velocity of bubbles,and the experimental results show that the laser pulse energy influences the volume and the rising velocity of the bubbles.In addition,some interesting phenomena are observed:when the laser pulse energy is between 1.6 μJ and 26 μJ,the bubble may split into two smaller ones with comparable size in the rising process;when the laser pulse energy is between 26 μJ and 600 μJ,the bigger bubble is generated accompanied by smaller bubbles.This research is helpful to the understanding of the fluid dynamics induced by filamentation in water.