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

In high-power laser systems, the primary cause of contamination of optical components and degradation of spatial cleanliness is laser-induced sputtering of particles. To mitigate this problem, laminar flow is frequently utilized to control the direction and transport of these particles. This study characterizes the properties of laser-induced sputtering particles, including their flying trend, diameter range, and velocity distribution at varying time intervals. A time-resolved imaging method was employed to damage the rear surface of fused silica using a 355 nm Nd: YAG pump laser. The efficacy of laminar flow in controlling these particles was then assessed, with a particular focus on the influence of laminar flow direction, laminar flow velocity, particle flight height, and particle diameter. Our results indicate that the optimal laminar flow velocity for preventing particle invasion is highly dependent on the maximum particle attenuation distance (or safety distance), which can vary by up to two orders of magnitude. Furthermore, a laminar flow velocity of 0.5 m/s can effectively prevent particle sedimentation. Future research will aim to optimize laminar flow systems based on these findings to achieve high surface cleanliness in high-power laser systems with minimal energy consumption.