Analyzing the mechanisms of deposition and oxygen plasma-based cleaning of vacuum laser-induced contamination

Laser-Induced Contamination (LIC) is an effect characterized by the formation of organic, nanometric and performance degrading deposits on irradiated optics. LIC is common with lasers operating in vacuum, and poses risks, particularly for space and quantum optics applications. This study investigates the mechanisms of deposition and oxygen plasma cleaning of LIC deposits under 355 nm laser irradiation on fused silica using a combination of in-situ and ex-situ characterization techniques. ToF-SIMS and Raman spectroscopy results evidence a continuous evolution of the chemical composition of LIC deposits under irradiation, with fully developed “donut” deposits featuring graphite-like carbon in the crater and heavy organic polymers at the rim. Gas-phase mass spectrometry, pressure, transmission, and fluorescence results provide more detailed information on the LIC deposit cleaning using a laser activated oxygen-based plasma. These findings lay a solid foundation towards building a model that quantitatively describes the LIC effect.