Paper
30 December 2019 High precision measurement of optical absorption in low-OH fused silica at 2 micron
Craig Ingram, Huy Tuong Cao, Sebastian Ng, Daniel D. Brown, David Ottaway, Peter Veitch, Adam Gambell, Nikita Simakov, Alexander Hemming
Author Affiliations +
Abstract
The first detection of gravitational waves from a binary black hole inspiral by LIGO in September 2015 heralded the beginning of a new age in gravitational wave astronomy. The detection of a binary neutron inspiral in August 2017 and has now opened up a new era of multi-messenger astronomy. To increase the sensitivity of future gravitational wave detectors, a change to cryogenic silicon test masses and an increase in laser power may be required. Silicon is a compelling choice as it has high thermal conductivity at cryo- genic temperatures, which reduces temperature gradients generated by optical absorption. Additionally, at 123 K, its thermal expansion coefficient crosses zero. Thus, near this temperature, thermo-elastic distortion of the mirror surface should be drastically reduced, as would the effect of thermo-elastic noise due to thermodynamic temperature fluctuations. However, the adoption of silicon for the optical substrates would necessitate a shift of operating wavelength from 1064 nm to >1.3 μm where silicon is transparent. While potential wavelengths include ca. 1.55 μm and 2.0 μm, the longer wavelengths may be preferred due to lower scattering loss and coating absorption.
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Craig Ingram, Huy Tuong Cao, Sebastian Ng, Daniel D. Brown, David Ottaway, Peter Veitch, Adam Gambell, Nikita Simakov, and Alexander Hemming "High precision measurement of optical absorption in low-OH fused silica at 2 micron", Proc. SPIE 11200, AOS Australian Conference on Optical Fibre Technology (ACOFT) and Australian Conference on Optics, Lasers, and Spectroscopy (ACOLS) 2019, 1120031 (30 December 2019); https://doi.org/10.1117/12.2539961
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KEYWORDS
Adaptive optics

Absorption

Optical testing

Wavefront distortions

Precision measurement

Precision optics

Silica

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