Material loss angles from direct measurements of broadband thermal noise
We estimate the loss angles of the materials currently used in the highly reflective test-mass coatings of interferometric detectors of gravitational waves, namely Silica, Tantala, and Ti-doped Tantala, from direct measurement of coating thermal noise in an optical interferometer testbench, the Caltech TNI. We also present a simple predictive theory for the material properties of amorphous glassy oxide mixtures, which gives results in good agreement with our measurements on Ti-doped Tantala. Alternative measurement methods and results are reviewed, and some critical issues are discussed.
© 2015 American Physical Society. Received 27 August 2014. This work has been supported in part by the NSF under Cooperative Agreement No. PHY-0757058 and the Italian National Institute for Nuclear Physics (INFN) under the CSN-V COAT grant. Stimulating discussions with V. B. Braginsky, G. Cagnoli, R. Flaminio, P. Fritschel, G. Harry, K. Kuroda, J. M. Mackowski, I. Martin, N. Mio, and S. Penn are gratefully acknowledged.
Submitted - 1501.06371.pdf
Published - PhysRevD.91.022005.pdf