In situ observation of UV laser-induced deposit formation by fluorescence measurement

Abstract

We investigated the formation of UV laser induced deposits on uncoated and coated fused silica optics under vacuum conditions in presence of outgassing materials. As contamination samples epoxy, silicone and polyurethane containing materials were used. To realize low partial pressures of the contaminants in the gas phase they were slightly heated (40°C). The formation of the depositions was monitored in situ and online by detecting the fluorescence emission of the deposits, excited by the UV laser beam. The influence of different optical coatings on the deposit formation was studied. By analysing the surface profiles of the deposits, growth rates were estimated. Time-of-flight secondary ion mass spectroscopy was used for chemical characterization of the deposits.