The damage kinetics of the front surface of fused silica ablated by nanosecond laser

Abstract

The ablation experiments were carried out on the front surfaces of fused silica samples using nanosecond lasers with wavelengths of 355 and 532 nm, aiming to study the damage mechanism of nanosecond laser ablation of fused silica. The high time-resolved pump-probe shadowgraphy technique was used to record the shock waves and plasma phenomena induced by laser spot explosion. Based on the experimental data and the physical model of the point explosion theory, the characteristic curves of the radius, velocity, pressure, and temperature of the shock wave front as a function of the delay time were fitted. After processing the transient ablation plume images using relevant techniques, the luminescent area of the laser focusing region can be obtained, and then the distribution characteristics of the plasma intensity can be derived. The experimental results show that, compared with the 532 nm laser, when the 355 nm ultraviolet laser ablates the fused silica sample, both the growth amplitude and expansion speed of the generated shock wave radius are faster, and the plasma expansion velocity induced by the 355 nm laser is approximately 20% faster than that by the 532 nm laser, and the plasma brightness of the former is about 33.09% higher than that of the latter. Combined with the research results of shock wave and plasma characteristics, the evolution mechanism of plasma affecting the propagation characteristics of shock waves is disclosed. These are helpful to understand the interaction between laser and materials more deeply and provide a basis for optimizing laser parameters in laser engineering.