Mitigation of laser-induced contamination in vacuum in high-repetition-rate high-peak-power laser systems

• DOI: 10.1364/ao.414878
• Publication Date: 2020-12-16T16:23:34Z
• Authors: Zbyněk Hubka; Jakub Novák; Irena Majerová; Jonathan T. Green; Praveen K. Velpula; Robert Boge; Roman Antipenkov; Václav Šobr; Daniel Kramer; Karel Majer; Jack A. Naylon; Pavel Bakule; Bedřich Rus
• Keywords: 0103 physical sciences; 01 natural sciences; Allegra laser system

Vacuum chambers are frequently used in high-energy, high-peak-power laser systems to prevent deleterious nonlinear effects, which can result from propagation in air. In the vacuum sections of the Allegra laser system at ELI-Beamlines, we observed degradation of several optical elements due to laser-induced contamination (LIC). This contamination is present on surfaces with laser intensity above

30

G W

/

c m

2

with wavelengths of 515, 800, and 1030 nm. It can lead to undesired absorption on diffraction gratings, mirrors, and crystals and ultimately to degradation of the laser beam profile. Because the Allegra laser is intended to be a high-uptime source for users, such progressive degradation is unacceptable for operation. Here, we evaluate three methods of removing LIC from optics in vacuum. One of them, the radio-frequency-generated plasma cleaning, appears to be a suitable solution from the perspective of operating a reliable, on-demand source for users.