Optical studies of glass stability in fluoride glass systems: Intrinsic rayleigh scattering

Brillouin and Rayleigh scattering studies were done on various multicomponent halide glasses. The effect of addition of sodium in a ZBLA glass on the crystallization and light scattering behavior was investigated by comparing the optical behavior of two groups of fluorides, namely ZBLA and ZBLAN. Light scattering data from single component and multicomponent glasses were used to study the correlation of optical scattering with particles size. Evidence of phase separation of multicomponent halide glasses will be presented and discussed. An experimental study of the time dependent growth of concentration fluctuations during annealing shows that phase separation by means of a spinodal mechanism is possible for these glasses. In comparing the complex halide glasses to beryllium-fluoride glasses we observe intrinsic Rayleigh Scattering losses that are about the same magnitude. In attempting to stabilize the BeF2 glass against water attack by adding ThF4 a dramatic increase of the intrinsic Rayleigh scattering was observed.