Technological processing of silica as seen through laser-induced damage tests

Technological processing of bulk silica is needed at many points of the fabrication of optical components. In the Laser Integration Line (LIL) and Megajoule Laser (LMJ), with the usual but challenging optical constraints of keeping the wavefront quality on large optics the constraint of high flux laser resistance is added. This has led to many technological improvements of silica processing which have been transferred into the industrial tissue. Improved polishing and cleaning processes have been developed which avoid the contamination of surface with polishing agents and are now used for lenses, windows, and substrates preparation of mirrors and polarizers. But some components like the gratings which are to be used on LIL and LMJ need new processing steps which are typical of the semiconductor industry and whose effects are unknown in terms of laser induced damage threshold in silica surface and subsurface. After a summary of the specifications and the performances of these gratings at 1 and 3(omega) wavelength we will focus on the laser induced damage (LID) tests that were performed at different stages of the grating process and see how they impact on the LID threshold of the gratings.