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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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
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 (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