Anti-reflective thin films used on optics within the target chambers of high power lasers used for plasma physics experiments degrade significantly in use. The cause of this may not be attributed to any single influence. Coating from target debris, absorption of vacuum chamber vapors, and the exposure to vacuum conditions and X rays will all contribute. To simulate some of these conditions, sol-gel derived optical film ageing studies have been performed on a range of anti-reflective coatings over a 4-month period. Similarly the use of sol-gel High Reflectivity coatings for mirrors need to be durable and stable with time in their likely working environments. The coatings have been assessed with regard to their laser induced damage threshold (LIDT), transmission properties, refractive index and thickness at three wavelengths (355 nm, 532 nm and 1064 nm). Although exact replication of the conditions is impossible some of the parameters have been controlled including pressure and humidity as a function of time. We report on the changes experienced by these coatings under these conditions and discuss possible reasons for the observed trends and the effect this could have on coating selection.

Date Published: 12 April 2001
PDF: 9 pages
Proc. SPIE 4347, Laser-Induced Damage in Optical Materials: 2000, (12 April 2001); doi: 10.1117/12.425015

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)