Spatial sputtering of fused silica after a laser-induced exploding caused by a 355 nm nd: YAG laser

Abstract

To alleviate laser-induced threats in the high-power laser systems, it is necessary to understand the debris propagation process and distribution characteristics, then take protection and cleaning strategies to sustain an ultra-clean environment. This work presents an experimental investigation of the sputtering behaviors of the laser-induced fused silica debris to clarify their longitudinal propagation and bottom distribution on the millimeter scale. Two types of polished surfaces with more than three orders of magnitude differences in surface roughness were adopted. The result reveals the centralized/decentralized distribution and the ability of long-range movement of debris propelled by the melting and mechanical failure. The maximum largest dispersion angle (LDA) appears at 18J/cm2 for debris within 10–20 μm from the Two Sides polished surface; debris <30 μm dominate the major quantity in the longitudinal propagation, and their centralization ability profoundly relies on the laser fluence and the surface roughness of the target; the diameter of the debris with long-range movement generally below 20 μm. This study could guide for establishing the overall dynamic cleaning strategy inside the high-power laser systems.

Surface Cleanliness Maintenance with Laminar Flow Based on the Characteristics of Laser-Induced Sputtering Particles in High-Power Laser Systems

“…Out of these, only the longitudinal velocity of V 0 derived from the translational distance in the x-direction contributes to the particle’s direct invasion (as displayed in Figure 2 a). The remaining translational distances in the y and z directions, which arise due to factors such as energy deposition [ 11 ], temporal air acceleration caused by pressure gradient differences [ 50 ], and Basset history [ 51 ], only change the relative positions of particles before they reach the surface. Additionally, rotational movements of particles in all directions during flight, which result in changes in Magnus and Saffman lift forces [ 52 , 53 ], only further modify the translational distances in the y and z-directions.…”

“…The detailed mechanism of deceleration for large particles has been discussed in refs. [ 11 , 19 ] and will not be repeated in this work.…”

“…The second part, in contrast, is governed by the stable surrounding air and is described by Equation (5). As the first part only ranges from 1.7 to 3.8 mm ((integrate fit functions between 0 ns and 13,000 ns)), which is a small fraction of the total translational distance in the x-direction (beyond 72 mm [ 11 ]), the second part primarily influences the attenuation distance. Figure 5 a displays the attenuation distances of the particles over time, as calculated using the initial velocities obtained from the fit functions at 13,000 ns and Equation (5).…”

“…For scenario (2), laminar flow longitudinally entrains particles and prevents them from landing on the surface of the optics with an edge length of L . As laser-generated particles are primarily aerosols with diameters smaller than 50 μm [ 9 , 11 ], they are easily influenced by the flow, and their inertial effect along the x-direction can be disregarded. Additionally, the velocity of the laminar flow inside high-power laser systems is typically less than several meters per second [ 13 , 21 ].…”

“…One critical aspect of these consumptions is the usage of ancillary energy, which is mainly required to maintain a high standard of cleanliness in the workspace and on the surface of optical components [ 8 ]. This is because laser-induced pollutants present an unavoidable risk [ 9 , 10 , 11 ].…”