Laser-optics qualification for space applications

Abstract

Accessing space with high-power laser systems is not a straightforward task as the space environment entails various risks [1] for optical surfaces and even bulk materials. High-power laser systems can respond very sensitively on absorption increase on its manifold of optical surfaces or in the bulk of transmissive optics, on misalignment of the optical axis, or coating delamination or destruction. These deleterious effects can be conveyed by a simultaneous action of outgassing contaminants and (UV) laser radiation leading to absorbing deposits on optical surfaces, by high energy solar or cosmic radiation generating color centers in the bulk of materials, by vibration-sensitive mounting of optics leading to misalignment during launch, by high-fluence exposure exceeding vacuum laser damage thresholds (coating destruction) or mismatch of thermal expansion coefficients (coating delamination), to mention just the most important risks. Extensive tests are currently supported by ESA / ESTEC at various labs in Europe to find ways to dispose of or mitigate the risks mentioned above.