| We have carried out an experiment to test the theory of the thermo-optic response of a dielectric stack mirror coating and to measure parameters of interest in calculating thermo-optic noise. Specifically, we measured the coefficient of thermal expansion and the change of index of refraction with temperature (dn/dT ) for thin film silica (SiO2) and tantala (Ta2O5) in mirror coatings. These measurements were achieved by driving thermal fluctuations in such mirrors in one arm of a small Michelson interferometer. We report on the results of that experiment along with its potential implications for future gravitational wave detectors, and suggest next steps for this important line of investigation. |
