Thermoelastic-Damping Noise from Sapphire Mirrors in a Fundamental-Noise-Limited Interferometer

We report the first high-precision interferometer using large sapphire mirrors, and we present the first direct, broadband measurements of the fundamental thermal noise in these mirrors. Our results agree well with the thermoelastic-damping noise predictions of Braginsky, et al. [V. B. Braginsky, M. L. Gorodetsky, and S. P. Vyatchanin, Phys. Lett. A 264, 1 (1999)] and Cerdonio et al. [M. Cerdonio, L. Conti, A. Heidmann, and M. Pinard, Phys. Rev. D 63, 082003 (2001)], which have been used to predict the astrophysical reach of advanced interferometric gravitational wave detectors.