Cryogenic measurements of mechanical loss of high-reflectivity coating and estimation of thermal noise

We report on low-frequency measurements of the mechanical loss of a high-quality (transmissivity T < 5 ppm at lambda(0) = 1064 nm, absorption loss <0.5 ppm) multilayer dielectric coating of ion-beam-sputtered fused silica and titanium-doped tantala in the 10-300 K temperature range. A useful parameter for the computation of coating thermal noise on different substrates is derived as a function of temperature and frequency. (C) 2013 Optical Society of America