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arXiv · 2508.20043

Temperature induced optical scatter changes in titania-germania coatings

D. P. Kapasi·T. Counihan·J. R. Smith·S. Tait·G. Billingsley
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Abstract

Titania doped with tantala is the high index material (high n) for the optical coatings used in LIGO and Virgo and its thermal noise limits LIGO/Virgo observations of astrophysical sources. In this paper, we study temperature induced changes to optical scatter of a multilayer highly reflective coating comprised of silica (low n) and titania doped with germania (high n) as a potential candidate to reduce coating thermal noise in ground-based observatories operating at room temperature. We observe that the scatter measured at 8 degree in a small region is low, with a median starting BRDF of $1.1 \times 10^{-7}\,\mathrm{str}^{-1}$ increasing to $1.2 \times 10^{-6}\,\mathrm{str}^{-1}$ through annealing. The results presented here show the potential of adopting titania doped with germania coatings for future upgrades to LIGO and Virgo and as a pathfinder coating for Cosmic Explorer, a next-generation detector.

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D. P. Kapasi, T. Counihan, J. R. Smith, S. Tait, G. Billingsley. 2025-08-27. Temperature induced optical scatter changes in titania-germania coatings. https://arxiv.org/abs/2508.20043

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