Laser damage resistance of optical components in sub-picosecond regime in the infrared

A rasterscan procedure is set to determine laser-induced damage densities in sub-picosecond regime at 1053nm on high-reflective coatings. Whereas laser-induced damage is usually considered deterministic in this regime, damage events occur on these structures for fluences lower than their intrinsic Laser-Induced Damage Threshold (LIDT). Damage densities are found to be high even for fluences as low as 20% of the LIDT. Scanning Electron Microscope observations of these “under threshold” damage sites evidence ejections of defects, embedded in the dielectric stack. It brings a new viewpoint for the qualification of optical components and for the optimization of manufacturing processes of coatings.