Very-low-frequency light scattering in silica at low temperatures

Abstract

We report a study of the light scattered at low-frequency shifts (0.03-20 ${\mathrm{cm}}^{-1\mathrm{}}$) in a silica-core glass fiber at temperatures as low as 1.46 K. Although our data agree in regions of spectral overlap with those reported previously, they provide a more detailed examination extending down to ∼0.03 ${\mathrm{cm}}^{-1\mathrm{}}$ (including the Brillouin spectrum). Contrary to extrapolations by earlier workers based on higher-frequency data, we find no evidence of a central component due to scattering from two-level tunneling systems.