Physical Origin of Early Failure for Contaminated Optics

Andrew Brown, David Bernot, Albert Ogloza, Kyle Olson, Jeff Thomas, Joseph Talghader

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


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.

Original languageEnglish (US)
Article number635
JournalScientific reports
Issue number1
StatePublished - Dec 1 2019

Bibliographical note

Funding Information:
This research was funded by the Office of Naval Research Joint Technology Office (JTO); (N00014-12-1-1030), and (N00014-17-1-2438).

Publisher Copyright:
© 2019, The Author(s).


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