The effect of compositional variations on the properties of rare-earth doped Ge-S-I chalcohalide glasses

Undoped and Pr3+-doped GexSyIz glasses, with atomic concentrations of germanium 0.33 less than or equal to x less than or equal to 0.43 and iodine 0 less than or equal to z less than or equal to 20, respectively, were synthesized and their optical and thermal properties measured. These properties followed the same compositional trends as the binary GexS1-x glasses, for which 0.33 less than or equal to x less than or equal to 0.43. The compositional dependences of the absorption edge and rare-earth solubility in GexSyIz glasses can be presented with a single parameter p = (y + z/2)/x. Addition of iodine to the Ge-rich GexS1-x-base glass system resulted in increasing the optical bandgap energy and decreasing the glass transition temperature. Thermal stability of the GexSyIz glasses is a function of both S/Ge ratio and iodine concentration. XPS and Raman spectroscopic measurements were conducted to obtain information about the structural changes accompanying the compositional variations. Properties-structure correlations are discussed. The results of the present study were used for selection of a compositional range within the GexSyIz glass system with optimal properties required for Pr3+-doped fiber amplifier application. (C) 1997 Elsevier Science B.V.