Rayleigh scattering in sapphire test mass for laser interferometric gravitational-wave detectors I. Measurement of scattering attenuation coefficient

We give a theoretical estimate of the lower limit of Rayleigh scattering in sapphire crystals. We report measurements of scattering attenuation coeffi cient in sapphire at wavelengths of 633 and 1064 nm using an imaging measur ement technique. The measured scattering loss in sapphire is similar to 13 ppm/cm. Using sapphire as a mirror and beamsplitter substrate in laser inte rferometric gravitational-wave detectors, Rayleigh scattering losses are si milar in magnitude to estimates of mirror losses. However, the scattering l evel still remains higher than the theoretical limit because of the presenc e of impurities vacancies in the sapphire crystal. (C) 1999 Published by El sevier Science B.V. All rights reserved.