Lasers, as a key enabling technology, have entered the field of space applications for some time. Recent space missions such as Curiosity with ChemCam, Perseverance with SuperCam, ALADIN, and ATLID have on-board optical instruments that use or will use high-power nanosecond lasers to achieve performances unattainable otherwise. However, the lifetime of such instruments remains a critical and limiting factor due to an effect called "laser-induced contamination" (LIC). This phenomenon, particularly frequent with Ultraviolet lasers operating under vacuum, leads to the formation of organic, nanometric, and absorbing deposits on the irradiated optics compromising their performance and lifespan. Given that maintenance is impossible in space, understanding and preventing LIC become crucial to ensure the success of future space missions.

An experimental setup that simulates LIC generation conditions has been built and validated at Fresnel Institute. The setup comprises a nanosecond Nd:YAG laser emitting at 355 nm, directed towards a transparent UV optic placed in a thermally controlled vacuum chamber connected with a regulation valve to another chamber containing a material acting as a contaminant during outgassing. A CCD camera detects in situ laser-induced fluorescence (LIF), and photodiodes record transmission variations due to LIC deposit formation.

LIC deposit analysis relies on several complementary methods. Optical profilometry (SWLI) and LIF study the morphology and the bump-to-crater evolution, also showing that the deposits always mirror the laser beam shape. LIF shows a qualitative difference in chemistries between the border and crater, as the crater is non-fluorescent.

Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), coupled with a “number of shots” series at constant laser fluence allows chemical analysis at various stages of growth. This confirmed quantitatively that the chemistry evolves under irradiation and that the crater and border have different chemistries. Transmission measurements highlight challenges posed by LIC, particularly concerning space instruments performance.