Light scattering in heavy-metal fluoride glasses in infra-red spectral region

The light-scattering characteristics in heavy-metal fluoride glasses were measured directly for the first time in the infrared spectral region of interest for ultralow-loss optical-fibre applications using a tunable colour-centre laser as an excitation source. The total scattering coefficients obtained between wavelengths of 2.4 and 3.2 ¿m exhibit a typical Rayleigh ¿¿4 dependence and lie near the theoretically predicted intrinsic minimum values for these materials. In addition, light-scattering measurements in the visible spectral region performed independently at two research laboratories on the same glass specimen have not only confirmed this Rayleigh behaviour, but more importantly have established that high-optical-quality fluoride glasses possess total scattering loss 1/2 to 2/3 that of the best synthetic silicas.