Mitigation of laser-induced contamination in vacuum in high-repetition-rate high-peak-power laser systems
Preventing laser-induced contamination (LIC) is key for achieving a reliable long-term operation of high-power laser systems. Modern laser systems are often operated in a vacuum environment, either to avoid non-linear effects and absorption in air (e.g. in EUV lithography) or because it is required by the specific application (e.g. for space lasers and in many scientific experiments). Unfortunately, this vacuum operation comes at a price, since it enhances the outgassing of volatile organic molecules. These molecules can be absorbed on optical surfaces and form deposits that grow upon laser-irradiation and result in a degradation of system performance. In the featured publication, Hubka et al. from the ELI beamlines in Prague share results of their efforts to mitigate LIC on optics of the Allegra laser system. They explore different cleaning methods and find that in-situ radio-frequency (RF) generated plasma etching is very beneficial for enabling a reliable system operation. The article thereby addresses many important practical aspects such as the cleaning speed and the placement of the RF plasma source. This makes the article a “must-read” for anyone facing problems from laser-induced contamination and anyone who has the wish to never face them.