TiO2 doped Ta2O5 coatings grown by biased target ion beam deposition for gravitational wave detectors

ORAL

Abstract

Advanced LIGO employs as end masses high reflectance mirrors of alternating layers of SiO2 and Ta2O5 doped with 25% of TiO2. Doping Ta2O5 with 25% TiO2 decreased the mechanical loss which increased the sensitivity of the detector, but the physical reasons of this are still unknown. In this work we studied thin films of Ta2O5 doped with different TiO2 concentrations grown by biased target ion beam deposition to evaluate the effect of doping in the mechanical loss and to search for high index materials with improved performance for the upcoming upgrade of LIGO and future detectors.
The deposition system consists of a low energy ion source and metallic targets individually pulsed biased. Control of each target bias allows for mixing Ta2O5 and TiO2, with estimates of the doping obtained by x-ray photoelectron spectroscopy. Extensive characterization shows the films are nearly stoichiometric and dense, with an absorption loss at 1064 nm lower than 20 ppm. Mechanical loss was measured in as deposited coatings and after annealing. For all TiO2 concentrations the mechanical loss is reduced after annealing, reaching a minimum for around 20% TiO2 after annealing at 600 C comparable to state-of-the-art TiO2 doped Ta2O5.

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Presenters

  • Mariana Fazio

    Department of Electrical and Computer Engineering and NSF ERC for Extreme Ultraviolet Science and Technology, Colorado State University, Fort Collins, CO, USA, Department of Electrical and Computer Engineering, Colorado State University

Authors

  • Mariana Fazio

    Department of Electrical and Computer Engineering and NSF ERC for Extreme Ultraviolet Science and Technology, Colorado State University, Fort Collins, CO, USA, Department of Electrical and Computer Engineering, Colorado State University

  • Gabriele Vajente

    LIGO Laboratory, California Institute of Technology, Pasadena, CA, USA, LIGO Laboratory, California Institute of Technology

  • Alena Ananyeva

    LIGO Laboratory, California Institute of Technology, Pasadena, CA, USA, California Institute of Technology, LIGO Laboratory, California Institute of Technology

  • Eric Keith Gustafson

    LIGO Laboratory, California Institute of Technology, Pasadena, CA, USA, California Institute of Technology, LIGO Laboratory, California Institute of Technology, LIGO Lab, California Institute of Technology

  • Carl Lévesque

    Université de Montréal, Montréal, Quebec, Canada, Department of Physics, Université de Montréal

  • François Schiettekatte

    Université de Montréal, Montréal, Quebec, Canada, Department of Physics, Université de Montréal

  • Ashot Markosyan

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

  • Riccardo Bassiri

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

  • Martin Fejer

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

  • Carmen Susana Menoni

    Colorado State Univ, Department of Electrical and Computer Engineering and NSF ERC for Extreme Ultraviolet Science and Technology, Colorado State University, Fort Collins, CO, USA, Department of Electrical and Computer Engineering, Colorado State University