Amorphous silicon with extremely low absorption: beating thermal noise in gravitational astronomy

Birney, R. et al. (2018) Amorphous silicon with extremely low absorption: beating thermal noise in gravitational astronomy. Physical Review Letters, 121, 191101. (doi: 10.1103/PhysRevLett.121.191101)

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Amorphous silicon has ideal properties for many applications in fundamental research and industry. However, the optical absorption is often unacceptably high, particularly for gravitational-wave detection. We report a novel ion-beam deposition method for fabricating amorphous silicon with unprecedentedly low unpaired electron-spin density and optical absorption, the spin limit on absorption being surpassed for the first time. At low unpaired electron density, the absorption is no longer correlated with electron spins, but with the electronic mobility gap. Compared to standard ion-beam deposition, the absorption at 1550 nm is lower by a factor of ≈100. This breakthrough shows that amorphous silicon could be exploited as an extreme performance optical coating in near-infrared applications, and it represents an important proof of concept for future gravitational-wave detectors.

Item Type:Articles
Additional Information:Also supported by STFC grants ST/N005406/1 and ST/M006913/1.
Glasgow Author(s) Enlighten ID:Sproules, Dr Stephen and Bell, Dr Angus and Reid, Professor Stuart and Steinlechner, Dr Jessica and Tait, Dr Simon and Rowan, Professor Sheila and Martin, Dr Iain and Tornasi, Zeno and Hough, Professor James
Authors: Birney, R., Steinlechner, J., Tornasi, Z., MacFoy, S., Vine, D., Bell, A.S., Gibson, D., Hough, J., Rowan, S., Sortais, P., Sproules, S., Tait, S., Martin, I.W., and Reid, S.
College/School:College of Science and Engineering > School of Chemistry
College of Science and Engineering > School of Physics and Astronomy
Research Centre:College of Science and Engineering > School of Physics and Astronomy > Institute for Gravitational Research
Journal Name:Physical Review Letters
Publisher:American Physical Society
ISSN (Online):1079-7114
Copyright Holders:Copyright © 2018 American Physical Society
First Published:First published in Physical Review Letters 121:191101
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
624341Investigations in Gravitational Radiation / Particle Astrophysics Capital equipmentSheila RowanScience & Technology Facilities Council (STFC)ST/L000946/1S&E P&A - PHYSICS & ASTRONOMY
591721Optical characterisation of silicon and mirror materials for gravitational astronomy.Iain MartinThe Royal Society (ROYSOC)RG110331S&E P&A - PHYSICS & ASTRONOMY