Low Mechanical Loss ${\mathrm{TiO}}_{2}:{\mathrm{GeO}}_{2}$ Coatings for Reduced Thermal Noise in Gravitational Wave Interferometers

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, François Schiettekatte, and Carmen S. Menoni

Phys. Rev. Lett. 127, 071101 – Published 10 August 2021

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 $1 \times 10^{- 4}$ , low enough to provide improvement of almost a factor of 2 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 (Laser Interferometer Gravitational-Wave Observatory) and Virgo detectors.

Received 26 March 2021
Revised 23 June 2021
Accepted 14 July 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.071101

Physics Subject Headings (PhySH)

Gravitational wave detection

Amorphous materials Glasses Thin films

Condensed Matter, Materials & Applied PhysicsGravitation, Cosmology & AstrophysicsGeneral Physics

Authors & Affiliations

Gabriele Vajente ^1,*, Le Yang ², Aaron Davenport³, Mariana Fazio³, Alena Ananyeva¹, Liyuan Zhang¹, Garilynn Billingsley¹, Kiran Prasai⁴, Ashot Markosyan⁴, Riccardo Bassiri ⁴, Martin M. Fejer⁴, Martin Chicoine⁵, François Schiettekatte ⁵, and Carmen S. Menoni^2,3

¹LIGO Laboratory, California Institute of Technology, Pasadena, California 91125, USA
²Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
³Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, USA
⁴Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA
⁵Département de Physique, Université de Montréal, Montréal, Québec H3T 1J4, Canada