Physical Origin of Early Failure for Contaminated Optics

Laser-Induced optical breakdown often occurs unexpectedly at optical intensities far lower than those predicted by ultra-short pulse laser experiments, and is usually attributed to contamination. To determine the physical mechanism, optical coatings were contaminated with carbon and steel microparti...

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Bibliographic Details
Published in:Scientific reports 2019-01, Vol.9 (1), p.635-635, Article 635
Main Authors: Brown, Andrew, Bernot, David, Ogloza, Albert, Olson, Kyle, Thomas, Jeff, Talghader, Joseph
Format: Article
Language:English
Subjects:
639/624/1075
639/624/399
639/624/400
Absorption
Contamination
Heat transfer
Humanities and Social Sciences
Lasers
Microparticles
multidisciplinary
Optics
Science
Science (multidisciplinary)
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Summary:Laser-Induced optical breakdown often occurs unexpectedly at optical intensities far lower than those predicted by ultra-short pulse laser experiments, and is usually attributed to contamination. To determine the physical mechanism, optical coatings were contaminated with carbon and steel microparticles and stressed using a 17 kW continuous-wave laser. Breakdown occurred at intensity levels many orders of magnitude lower than expected in clean, pristine materials. Damage thresholds were found to strongly follow the bandgap energy of the film. A thermal model incorporating the particle absorption, interface heat transfer, and free carrier absorption was developed, and it explains the observed data, indicating that surface contamination heated by the laser thermally generates free carriers in the films. The observed bandgap dependence is in direct contrast to the behavior observed for clean samples under continuous wave and long-pulse illumination, and, unexpectedly, has similarities to ultra-short pulse breakdown for clean samples, albeit with a substantially different physical mechanism.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-018-37337-5