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New heavy halide glasses without fluorine have been synthesized as Pr3+ host materials for optical amplification at 1.3 micrometers or other active applications which require a phonon energy as low as possible. A relatively stable composition is 15CdCl2-10CdI2- 20PbI2-40PbBr2-15CsBr. However, this glass still undergoes the devitrification during fiber drawing process. A small amount of oxides and sulfides have been introduced in this system to decrease the crystallization tendency. The incorporation of 3 mole percent PbO in the base glass composition enlarges the thermal stability range. The stabilizing effect of CdO is more limited than that of PbO. Optimum results are observed when PbO substitutes PbBr2 rather than PbI2. The influence of several sulfides on glass stability was also investigated in the same glass. The additions of 5 mole percent of HgS, As2S3 and Sb2S3 appear favorable to glass formation. By comparison, attempts implemented with SeS2, PbS and CdS had no significant effect. An additional benefit of the introduction of oxides and sulfides is the decrease of the hygroscope character of the base glass. The optical transmission in the visible-IR spectrum shows no absorption at the pump and emission wavelengths, e.g. 1.0 and 1.3 micrometers , while the cut-off wavelength exceeds 10 micrometers for sample of 3 mm in thickness.
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