Optical properties of germania and titania at 1064 nm and at 1550 nm

• DOI: 10.1088/1361-6382/ad3c8c
• Publication Date: 2024-04-09T23:00:54Z
• Authors: D Diksha; A Amato; V Spagnuolo; G I McGhee; M Chicoine; C Clark; S Hill; J Hough; R Johnston; R Keil; N Mavridi; S Reid; S Rowan; T Schapals; F Schiettekatte; S C Tait; I W Martin; J Steinlechner
• Keywords: coating thermal noise; Physics; 0103 physical sciences; gravitational-wave detectors; titania; low temperature; THERMAL NOISE; FILMS; 530; absorption

Abstract One of the main noise sources in current gravitational-wave detectors is thermal high-reflectivity coatings on interferometer optics. Coating dominated by mechanical loss high-refractive index material within coating stacks, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>Ta</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>5</mml:mn> </mml:mrow> </mml:math> mixed with <mml:mi>TiO</mml:mi> . For upgrades to room-temperature detectors, a mixture <mml:mi>GeO</mml:mi> and an interesting alternative candidate material. While rather low refractive GeO 2 increases increasing content, higher content results lower threshold temperature before heat treatment leads crystallisation, potentially degradation optical properties. future cryogenic other hand, beneficial as TiO suppresses low-temperature peak In this paper, we present properties coatings—produced plasma-assisted ion-beam evaporation—with high at 1550 nm, laser wavelength considered for function heat-treatment temperature. comparison, absorption pure was also measured. Furthermore, currently-used 1064 nm are presented.