Low mechanical loss TiO$_2$:GeO$_2$ coatings for reduced thermal noise in Gravitational Wave Interferometers

Gabriele Vajente; Le Yang; Aaron Davenport; Mariana Fazio; Alena Ananyeva; Liyuan Zhang; Garilynn Billingsley; Kiran Prasai; Ashot Markosyan; Riccardo Bassiri; Martin M. Fejer; Martin Chicoine; Francois Schiettekatte; Carmen S. Menoni

doi:10.1103/PhysRevLett.127.071101

paper

Low mechanical loss TiO $_{2}$ :GeO $_{2}$ coatings for reduced thermal noise in Gravitational Wave Interferometers

arXiv:2108.04954 · doi:10.1103/PhysRevLett.127.071101

Abstract

The sensitivity of current and planned gravitational wave interferometric detectors is limited, in the most critical frequency region around 100 Hz, by a combination of quantum noise and thermal noise. The latter is dominated by Brownian noise: thermal motion originating from the elastic energy dissipation in the dielectric coatings used in the interferometer mirrors. The energy dissipation is a material property characterized by the mechanical loss angle. We have identified mixtures of titanium dioxide (TiO $_{2}$ ) and germanium dioxide (GeO $_{2}$ ) that show internal dissipations at a level of 1 $\times 1 0^{- 4}$ , low enough to provide almost a factor of two improvement on the level of Brownian noise with respect to the state-of-the-art materials. We show that by using a mixture of 44% TiO $_{2}$ and 56% GeO $_{2}$ in the high refractive index layers of the interferometer mirrors, it would be possible to achieve a thermal noise level in line with the design requirements. These results are a crucial step forward to produce the mirrors needed to meet the thermal noise requirements for the planned upgrades of the Advanced LIGO and Virgo detectors.

Low mechanical loss TiO $_{2}$ :GeO $_{2}$ coatings for reduced thermal noise in Gravitational Wave Interferometers

Abstract

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Low mechanical loss TiO2​:GeO2​ coatings for reduced thermal noise in Gravitational Wave Interferometers

Abstract

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Low mechanical loss TiO $_{2}$ :GeO $_{2}$ coatings for reduced thermal noise in Gravitational Wave Interferometers