Localized silica re-fusion for laser damage mitigation

A continuous CO 2 laser is used to locally re-fuse silica and avoid growth of 3ω laser damaged sites. Temperature evolution on each spot is monitored by a radiometry diagnostic. Important temperature variations are observed from site to site at a mm scale. Such variations can only be induced by a non homogeneous, high temperature, thermal conductivity. Real time retroaction, on silica exposure to laser radiation, enables us to control surface silica evaporation and etching depth. The 3ω laser induced damage threshold test of the re-fused sites shows that the limit for the mitigation rate lies in the surrounding silica surface.