Current interferometric gravitational wave detectors use test masses with mirror coatings formed from multiple layers of dielectric materials, most commonly alternating layers of SiO2 (silica) and Ta2O5 (tantala). However, mechanical loss in the Ta2O5/SiO2 coatings may limit the design sensitivity for advanced detectors. We have investigated sources of mechanical loss in the Ta2O5/SiO2 coatings, including loss associated with the coating-substrate interface, with the coating-layer interfaces, and with the bulk material. Our results indicate that the loss is associated with the bulk coating materials and that the loss of Ta2O5 is substantially larger than that of SiO2.
@article{arxiv.gr-qc/0302093,
title = {Mechanical Loss in Tantala/Silica Dielectric Mirror Coatings},
author = {Steven D. Penn and Peter H. Sneddon and Helena Armandula and Joseph C. Betzwieser and Gianpietro Cagnoli and Jordan Camp and D. R. M. Crooks and Martin M. Fejer and Andri M. Gretarsson and Gregory M. Harry and Jim Hough and Scott E. Kittelberger and Michael J. Mortonson and Roger Route and Sheila Rowan and Christophoros C. Vassiliou},
journal= {arXiv preprint arXiv:gr-qc/0302093},
year = {2009}
}