We present the results of mechanical characterizations of many different high-quality optical coatings made of ion-beam-sputtered titania-doped tantala and silica, developed originally for interferometric gravitational-wave detectors. Our data show that in multi-layer stacks (like high-reflection Bragg mirrors, for example) the measured coating dissipation is systematically higher than the expectation and is correlated with the stress condition in the sample. This has a particular relevance for the noise budget of current advanced gravitational-wave interferometers, and, more generally, for any experiment involving thermal-noise limited optical cavities.
@article{arxiv.1511.06172,
title = {Mechanical loss in state-of-the-art amorphous optical coatings},
author = {Massimo Granata and Emeline Saracco and Nazario Morgado and Alix Cajgfinger and Gianpietro Cagnoli and Jérôme Degallaix and Vincent Dolique and Danièle Forest and Janyce Franc and Christophe Michel and Laurent Pinard and Raffaele Flaminio},
journal= {arXiv preprint arXiv:1511.06172},
year = {2016}
}