Inverse-Power-Law Light Scattering in Fused-Silica Optical Fiber

The quasielastic light-scattering spectrum of cooled fused-silica optical fibers has been measured by heterodyne spectroscopy in the frequency range 75 kHz to 75 MHz at temperatures from 20 to 293 K. Below 160 K, the conventional Rayleigh scattering becomes undetectable and the main scattering component has a spectrum given by $S(\omega ,T)\sim {\omega }^{-\alpha }$, where $0.5<\mathrm{}\alpha \mathrm{}\left(T\right)<1\mathrm{}$. The scattered power has the temperature dependence expected for activated structural transitions.