New insight into defect-induced laser damage in UV multilayer coatings

Michael Reichling; Axel Bodemann; Norbert Kaiser

doi:10.1117/12.213713

14 July 1995 New insight into defect-induced laser damage in UV multilayer coatings

Michael Reichling, Axel Bodemann, Norbert Kaiser

Proceedings Volume 2428, Laser-Induced Damage in Optical Materials: 1994; (1995) https://doi.org/10.1117/12.213713
Event: Laser-Induced Damage in Optical Materials: 1994, 1994, Boulder, CO, United States

Abstract

High performance AL₂O₃/SiO₂ mirror coatings for 248 nm have been investigated with respect to their excimer laser damage resistivity. Global damage thresholds (in the range of 10-20 J/cm²) averaged over large areas were determined with the pulsed photoacoustic mirage detection method. With a raster scanning technique utilizing the same detection scheme, the local damage behavior was studied with 100 micrometers spatial resolution. It was found that the local damage threshold at specific sites was lower than the global damage threshold and it was assumed that this phenomenon was associated with micrometer-scale defects in the multilayer coating. To test this hypothesis photothermal displacement microscopy with micrometers lateral resolution was performed on the investigation regions prior to excimer laser light irradiation. Photothermal images revealed an extremely small background absorption and a small number of absorbing defect sites. For a number of such sites a clear correlation between the local absorption and the onset of laser damage at that specific location was found. We conclude that the crucial factor determining the damage resistivity of the high quality coating systems are defects and contaminants and that it will be possible to predict their damage thresholds by a complete microscopic photothermal inspection.

Citation Download Citation

Michael Reichling, Axel Bodemann, and Norbert Kaiser "New insight into defect-induced laser damage in UV multilayer coatings", Proc. SPIE 2428, Laser-Induced Damage in Optical Materials: 1994, (14 July 1995); https://doi.org/10.1117/12.213713

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