Laser-induced contamination mitigation on the ALADIN laser for ADM-Aeolus

Abstract

Laser-induced contamination (LIC) is a phenomenon that can lead to the degradation of the properties of optical components in vacuum due to the formation of deposits in the area irradiated by a laser beam. The deposit growth is proposed to be the result of photochemical and photothermal mechanisms triggered by the interaction of UV laser radiation and outgassing species from polymeric materials on the surface of the optics. In the framework of ESA's ADM-Aeolus satellite mission, a successful test campaign has been performed, which has demonstrated the efficiency of several mitigation techniques against LIC for the ALADIN laser. These include the standard contamination control methods of identification of materials with particular propensity to cause LIC, reduction of the outgassing of organic materials by vacuum bakeout and shielding of optical surfaces from contamination sources as well as novel methods such as in-situ cleaning. These methods are now being applied at satellite level in order to guarantee the success of the mission. The subject of this paper is to summarise the various mitigation techniques from the large number of studies that have been performed and is applicable to any use of high power pulsed lasers in vacuum in the presence of organic contaminants.