Review of tellurite glasses purification issues for mid-IR optical fiber applications

We reviewed the tellurite glass purification studies performed over the last 20 years, in particular dealing with the mid-infrared (mid-IR) transmission performances. Best results are obtained under rich O(2)atmosphere with platinum crucibles although Gibbs energy calculations show that other crucibles material are possible such as gold or alumina. From the point of view of the thermodynamics of involved oxidation reactions only, we identified the suitable conditions based on Gibbs energy calculations to be a synthesis temperature set above 900 K and a O(2)pressure around 10(5) Pa. The performances of the different purification techniques were also compared. Finally, we analyzed the tellurite fibers recently optimized for mid-IR which present low attenuation up to 4 mu m allowing supercontinuum generation up to 5 mu m.