Mechanical ringdown studies of large-area substrate-transferred GaAs/AlGaAs crystalline coatings

• DOI: 10.1364/josab.36.000c15
• Publication Date: 2019-01-31T16:30:03Z
• Authors: Steven D. Penn; Maya M. Kinley-Ha...; Ian A. O. MacMillan; Paula Heu; David Follman; Christoph Deutsch; Garrett D. Cole; Gregory M. Harry
• Keywords: Condensed Matter - Materials Science; 0103 physical sciences; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; General Relativity and Quantum Cosmology (gr-qc); 01 natural sciences; General Relativity and Quantum Cosmology

We investigated elastic loss in GaAs/AlGaAs multilayers to help determine the suitability of these coatings for future gravitational wave detectors. measured large ($\approx 70$-mm diameter) substrate-transferred crystalline coating samples with an improved substrate polish and bonding method. The loss, when decomposed into bulk shear contributions, was shown arise entirely from $\phi_{\mathrm{Bulk}} = (5.33 \pm 0.03)\times 10^{-4}$, $\phi_{\mathrm{Shear}} (0.0 5.2) \times 10^{-7}$. These results predict 8-mm diameter a 35-mm long cavity 250-$\mu$m spot size (radius) be $\phi_{\mathrm{coating}} (4.78 0.05) 10^{-5}$, agreement published result direct thermal noise measurement (4 4) 10^{-5}$. Bonding defects were have little impact on overall loss.