The spectroscopic quality factor (χ) found to be 1.52 forTZNTEr10 glass, which is higher than TeO2–ZnO–ZnF2 (TZF16) [6], Na2O–Nb2O5–TeO2 (NNT) [10], TeO2–ZnO–PbO–PbF2–Na2O (TZPPN) [34], TeO2–BaF2–Na2O (TBNE–1e) [35], B2O3–ZnO–TeO2 (1ErTB) [36] and lowerthan TeO2–P2O5–Al2O3–La2O3 [4], TeO2–ZnO–ZnF2 (TZF35) [6], and TeO2–ZnO–ZnF2–Na2O (ETZ) [33]. This is an important predictor for stimulated emission in a laser active medium [37], initially representedforNd3þ ion [38] and later used for evaluating all of the lasing ions.