Abstract

The output intensity of modern high-peak power Tksapphire lasers after the pulse recompression reaches the value of 10¹² W/cm². The diffraction gratings are mounted in a vacuum chamber of the compressor. In these conditions the diffraction gratings and other gold coated mirrors illuminated by the laser beam are subjected to carbon contamination, especially on the place of the output beam. This reduces diffraction efficiency of the compressor, introduces additional energy deposition on the surface of the diffraction grating thus possibly inducing irreversible changes of the diffraction grating structure. The deposition of the carbon layer on the grating surface takes place in an oil-free pumping conditions also. We think that in this case the CO₂ molecules attached to the grating surface and especially ‘hidden’ in the grooves are ionized under the influence of the high laser intensity. Recombination of the carbon atoms leads to a deposition of the carbon layer in the grating groves and hills.

© 2002 Optical Society of America