Study on the Ejection and Dispersion of Particles During the Damage Growth of Fused Silica Induced by Centimeter Level Aperture High Fluence Laser Beam

Abstract

Particle pollutants from laser-induced damage splash pose a serious threat to high-fluence laser systems. However, the ejection and dispersion of splashing particles in the system are not well understood. In this paper, an experimental method combining time-resolved pump-probe imaging and continuous imaging techniques is used to capture in detail the entire relaxation dynamics of splashing from the ejection to dispersion of laser-induced damage on fused silica rear surface over a larger time scale compared to previous transient studies; the morphology and kinematic properties of splashing particles accompanying the occurrence and continuous development of laser induced damage during the operation of centimeter level aperture high-fluence laser systems are studied by combining microscopic imaging, as well as the correlation between these behavioral properties and the degree of damage and destruction. The results indicate that the thermodynamic effect during the damage splashing process leads to the ejection of particles with different properties, and the difference in air viscosity force experienced by the particles is the reason for their different motion trajectories. Empirical formulas based on fluid mechanics can predict the distance of particle spraying well, which shows that particles with larger size and initial velocity move farther. During the process of laser damage growth, the increase in laser fluence leads to an increase in the velocity of small-sized particles, while the velocity of large particles and the splashing volume are related to the growth rate of the damaged area.

Keywords: Laser-induced damage, fused silica, material ejection, damage growth