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

Abstract

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.

Combined molecular and metallic particulate laser-induced contamination testing: de-risking activity for the LISA space mission

“…Considering this, LIC seems to be less of a concern for the LISA mission (1064nm, continuous-wave (cw), 150W/cm 2 ). Nonetheless, LIC did occur in the near-infrared (NIR) in multiple experimental studies [9,10,11] and the long mission duration, the financial and scientific significance of the mission, the lack of studies regarding the impact of potentially small deposits on the wavefront [12] and the estimation of the LISA working group that even a 2 nm deposit will start affecting the detection performance adversely (see Figure 1), lead to the conclusion that a comprehensive de-risking activity is crucial.…”

Reaction analysis and the removal mechanism of organic contaminants in plasma cleaning: a molecular dynamics simulation

“…[3][4][5] High-repetition-rate and high-peak-power lasers have been observed to induce materials to release volatile compounds and give rise to laser-induced contamination (LIC). 6 Physical characteristics of PCGs utilized in chirped pulse amplification (CPA) systems have been evolving towards larger dimensions to effectively decrease the luminous flux per unit area, 7 meanwhile this trend has led to an increased susceptibility of PCGs to organic LIC, exacerbating the cleaning challenges associated with their maintenance. Organic contaminants must be removed from the optics promptly to prevent potential damage.…”

Analysis of grating surface organic contamination in chirped pulse amplification system

“…Researchers found the organic contaminants on the surface of optical components were identified as paraffin oil and Dibutyl Phthalate (DBP) by GC/MS method in the LFEX facility, and this conclusion was also verified in other facilities [21][22][23] . Further studies by scholars found that organic contaminants on the surface of the deposited optical components were carbonized under an ultra-short pulse laser to form organic residual contaminants, also known as "carbon black" [24] . Organic residual contaminants are carbon nanoparticles composed of atoms such as hydrocarbon and oxygen, generally considered organic contaminants in their molecular content.…”