1064-nm, nanosecond laser mirror thin film damage competition

Abstract

This year’s competition aimed to survey state-of-the-art near-IR high reflectors. The requirements of the coatings were a minimum reflection of 99.5% at 0 degrees incidence angle light at 1064-nm. The choice of coating materials, design, and deposition method were left to the participants. Laser damage testing was performed at a single testing facility using the ISO standard protocol with a 3-ns pulse length laser system operating at 5 Hz in a multi-longitudinal mode. A double blind test assured sample and submitter anonymity. The damage performance results (LIDT) and sample rankings are compared to last year’s competition results where raster scanning test protocol was involved. In addition, details of the deposition processes, coating materials and substrate cleaning method are also shared. We found that hafnia/silica multilayer coatings deposited by e-beam are the most damage resistant under the test conditions. LIDT differences between testing protocols were up to 38 J/cm2, with ISO-reported LIDT results generally higher than those determined by raster scanning.