For the contaminated large-aperture vacuum separator coated with SiO2 sol-gel antireflection film in the facility, a Nd: YAG pulsed laser with a wavelength of 355 nm was performed in laser cleaning experiment. The experiment adopted a single-shot laser dry cleaning and a laser cleaning system assisted by an airflow replacement system. The experimental results suggest that there is an optimal process window for laser in-situ cleaning of optics. The optimal laser energy density for dry laser cleaning is 1.71 J/cm2, and the total particle removal rate is 57.67%. After using the airflow assisted laser cleaning process, the total particle removal rate is increased to 82.21%, which is improved by 24.54%, and it can effectively achieve complete removal of particles over 5 μm in diameter. Additionally, the optical microscope analysis results show that adding an airflow displacement system will not affect the substrate laser damage threshold. The result indicates that the airflow displacement assisted laser cleaning can effectively improve its cleaning effect and reduce the particle re-adhesion.
Efficient removal of SiO2 contaminated particles from sol-gel SiO2 filmed fused silica surface was achieved by single shot dry laser cleaning and airflow displacement system assisted laser cleaning using a Q switched Nd:YAG pulse laser at 355 nm in wavelength. The experiment result shows that for single-shot laser dry cleaning of sol-gel film fused silica samples under the condition of satisfying the theoretical cleaning threshold, the optimal laser energy density was 2.28 J/cm2, which is different from the process parameters of uncoated fused silica. In the optimal process parameters, single shot laser cleaning had obvious cleaning effect on SiO2 particles with particle diameter larger than 1 μm, and the removal ratio was 64.81%. When the density of particle was too high, the cleaning effect was weakened and the damage to the substrate was caused. The re-attachment of crushed particles also leaded to making the cleaning effect worse. The airflow displacement system assisted laser cleaning method further enhanced the effect of removing the optical surface contaminated particles and the decontamination efficiency was improved to 80.53% at 1.71 J/cm2. Our results demonstrated that airflow displacement system will be useful for single shot dry laser cleaning of SiO2 particles on an optical surface of fused silica.
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