Laser Cleaning Techniques for Removing Surface Particulate Contaminants on Sol-Gel SiO₂ Films

Dry laser cleaning (DLC) and laser shockwave cleaning (LSC) are used to remove the particulate contamination from SiO₂ sol−gel optical films. The results show that the LSC with a shockwave initiated by plasma formation under a focused laser beam pulse offers much better efficiency than DLC. Silica particles up to 10 µm on SiO₂ films can be removed without substrate damage at a gap distance of 0.5 mm, and a more uniform surface microstructure can be obtained after LSC. Furthermore, it is demonstrated that the transmittance of contaminated SiO₂ films can be restored to the as-deposited value after the LSC on dispersed-particle zones. LSC has potential applications in engineering-oriented large components.