Influence of processing conditions on IR edge absorption in fluorohafnate and fluorozirconate glasses

The influence of processing conditions on the IR absorption edge of fluoride glasses with the composition 62 MF4 1b 33 BaF 2 1b 5 LaF 3 (M = Hf or Zr) is reported. At higher values of the absorption coefficient ( α > 1 cm −1), the IR edge is nearly independent of processing conditions and appears to be intrinsic. At lower values ( α < 1cm −1) extrinsic features attributed to oxide impurities appear; these are suppressed when glass melting is carried out in a reactive atmosphere of CCl 4. Comparison of our results for HfF 4- and ZrF 4 based glasses shows that substitution of HfF 4 for ZrF 4 shifts the IR edge to longer wavelengths, but the intrinsic absorption curves are nearly parallel over the frequency range investigated.