title: Wide-band direct measurement of thermal fluctuations in an interferometer.
abstract: We directly measured mechanical thermal fluctuations in mirrors over three decades of frequency range using a short-length Fabry-Perot interferometer. This is the first such measurement at wide off-resonant frequency band that is much lower than mechanical resonant frequencies. Theoretically, the mechanical fluctuation in mirrors had been thought to become the principal noise in precise interferometry, such as in gravitational wave detection. We identified the thermally induced noises in the interferometer, the so-called substrate Brownian noise, substrate thermoelastic noise, and coating Brownian noise.
authors.affiliation: Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. numata@t-munu.phys.s.u-tokyo.ac.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Numata
authors.forename: Masaki
authors.initials: M
authors.lastname: Ando
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Shigemi
authors.initials: S
authors.lastname: Otsuka
authors.forename: Kimio
authors.initials: K
authors.lastname: Tsubono