Cryogenic mechanical loss of a single-crystalline GaP coating layer for precision measurement applications

Murray, P. G. et al. (2017) Cryogenic mechanical loss of a single-crystalline GaP coating layer for precision measurement applications. Physical Review D, 95(4), 042004. (doi:10.1103/PhysRevD.95.042004)

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Abstract

The first direct observations of gravitational waves have been made by the Advanced LIGO detectors. However, the quest to improve the sensitivities of these detectors remains, and epitaxially grown single-crystal coatings show considerable promise as alternatives to the ion-beam sputtered amorphous mirror coatings typically used in these detectors and other such precision optical measurements. The mechanical loss of a 1 μm thick single-crystalline gallium phosphide (GaP) coating, incorporating a buffer layer region necessary for the growth of high quality epitaxial coatings, has been investigated over a broad range of frequencies and with fine temperature resolution. It is shown that at 20 K the mechanical loss of GaP is a factor of 40 less than an undoped tantala film heat-treated to 600 °C and is comparable to the loss of a multilayer GaP/AlGaP coating. This is shown to translate into possible reductions in coating thermal noise of a factor of 2 at 120 K and 5 at 20 K over the current best IBS coatings (alternating stacks of silica and titania-doped tantala). There is also evidence of a thermally activated dissipation process between 50 and 70 K.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Rowan, Professor Sheila and Martin, Dr Iain and Hough, Professor James and Bassiri, Mr Riccardo and Murray, Dr Peter
Authors: Murray, P. G., Martin, I. W., Craig, K., Hough, J., Rowan, S., Bassiri, R., Fejer, M. M., Harris, J. S., Lantz, B. T., Lin, A. C., Markosyan, A. S., and Route, R. K.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review D
Publisher:American Physical Society
ISSN:1550-7998
ISSN (Online):1550-2368
Published Online:17 February 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Physical Review D 95(4):042004
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
624341Investigations in Gravitational Radiation / Particle Astrophysics Capital equipmentSheila RowanScience & Technologies Facilities Council (STFC)ST/L000946/1S&E P&A - PHYSICS & ASTRONOMY