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Proceedings Paper

Laser conditioning characterization and damage threshold prediction of hafnia/silica multilayer mirrors by photothermal microscopy
Author(s): A. B. Papandrew; Christopher J. Stolz; Zhouling Wu; Gary E. Loomis; Steven Falabella
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Paper Abstract

Laser conditioning has been shown to improve the laser damage threshold of some optical coatings by greater than 2x. Debate continues within the damage community regarding laser-conditioning mechanisms, but it is clear that nodular ejection is one of the byproducts of the laser conditioning process. To better understand why laser conditioning is so effective, photothermal microscopy was used to measure absorption of coating defects before and after laser exposure. Although a modest absorption reduction was expected due to the lower electric field peaks within a pit and the absence of potentially absorbing nodular seeds, surprisingly, absorption reductions up to 150x were observed. Photothermal microscopy has also been successfully used to correlate laser-induced damage threshold and absorption of defects in hafnia/silica multilayer optical coatings. Defects with high absorption, as indicated by high photothermal signal, have low damage thresholds. Previously a linear correlation of damage threshold and defect photothermal signal was established with films designed and damage tested at 1(omega) (1053 nm) and Brewster's angle (56.4 degree(s)), but characterized by photothermal microscopy at 514.5 nm and near-normal angle of incidence (10 degree(s)). In this study coatings designed, characterized by photothermal microscopy, and damage tested at the same wavelength, incident angle, and polarization did not have a correlation between defect photothermal signal and absorption.

Paper Details

Date Published: 12 April 2001
PDF: 9 pages
Proc. SPIE 4347, Laser-Induced Damage in Optical Materials: 2000, (12 April 2001); doi: 10.1117/12.425049
Show Author Affiliations
A. B. Papandrew, Lawrence Livermore National Lab. (United States)
Christopher J. Stolz, Lawrence Livermore National Lab. (United States)
Zhouling Wu, Lawrence Livermore National Lab. (United States)
Gary E. Loomis, Lawrence Livermore National Lab. (United States)
Steven Falabella, Lawrence Livermore National Lab. (United States)


Published in SPIE Proceedings Vol. 4347:
Laser-Induced Damage in Optical Materials: 2000
Gregory J. Exarhos; Arthur H. Guenther; Mark R. Kozlowski; Keith L. Lewis; M. J. Soileau, Editor(s)

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