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Wide survey of Ta<sub>2</sub>O<sub>5</sub>-based mixed oxide coatings for gravitational wave detectors

ORAL

Abstract

Thermal noise is a fundamental limitation in optical interferometry experiments as thermally driven fluctuations cause variations in the optical path. The sensitivity of gravitational wave detectors, such as Advanced LIGO and Advanced Virgo, is affected by the thermal noise in the high-reflectivity mirrors of the end masses. These mirrors are multilayer stacks of alternating layers of TiO2:Ta2O5 and SiO2, with the main source of thermal noise being the mechanical loss of TiO2:Ta2O5.
Towards the goal of identifying other potential dopants that can further decrease the thermal noise, we carried out an extensive study of Ta2O5 doped with different oxides: Al2O3, HfO2, Nb2O5, Sc2O3, SiO2, TiO2, Y2O3, ZnO, and ZrO2. Films were grown by reactive sputtering with a 20% dopant cation concentration. The influence of the dopant on the structure, optical properties, crystallization temperature and mechanical loss was evaluated. We found that oxides with the lowest Gibbs free energy of formation, such as Sc2O3, inhibit the complete oxidation of the Ta2O5 phase. We identify dopants for which the material crystallizes as a ternary compound, such as TiO2 and ZnO, which can induce atomic mixing and reduce mechanical loss.

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Presenters

  • Mariana Fazio

    Colorado State University, Department of Electrical and Computer Engineering, Colorado State University, Department of Electrical and Computer Engineering, Colorado State University Fort Collins

Authors

  • Mariana Fazio

    Colorado State University, Department of Electrical and Computer Engineering, Colorado State University, Department of Electrical and Computer Engineering, Colorado State University Fort Collins

  • Le Yang

    Colorado State University, Department of Chemistry, Colorado State University, Department of Chemistry, Colorado State University Fort Collins

  • Gabriele Vajente

    California Institute of Technology, LIGO Laboratory, California Institute of Technology, Caltech

  • Alena Ananyeva

    California Institute of Technology, LIGO Laboratory, California Institute of Technology, Caltech

  • GariLynn Billingsley

    California Institute of Technology, LIGO Laboratory, California Institute of Technology, Caltech

  • Ashot Markosyan

    Stanford University, Department of Applied Physics, Ginzton Laboratory, Stanford University, Edward L. Ginzton Laboratory, Stanford University

  • Riccardo Bassiri

    E. L. Ginzton Laboratory, Stanford University, Stanford University, Department of Applied Physics, Ginzton Laboratory, Stanford University, Edward L. Ginzton Laboratory, Stanford University, E.L. Ginzton Laboratory, Stanford University

  • Martin M. Fejer

    E. L. Ginzton Laboratory, Stanford University, Stanford University, Department of Applied Physics, Ginzton Laboratory, Stanford University, Edward L. Ginzton Laboratory, Stanford University, E.L. Ginzton Laboratory, Stanford University

  • Carmen Susana Menoni

    Colorado State University, Department of Electrical and Computer Engineering, Department of Chemistry, Colorado State University, Department of Electrical and Computer Engineering, Colorado State University Fort Collins