Improvement of 4 I 11/2 → 4 I 13/2 Transition Rate and Thermal Stabilities in Er 3+ ‐Doped TeO 2 ‐B 2 O 3 (GeO 2 )‐ZnO‐K 2 O Glasses

Spectroscopic and thermal analysis indicates that tellurite glasses doped with B 2 O 3 and GeO 2 are promising candidate host materials for wide‐band erbium doped fiber amplifier (EDFA) with a high 980 nm pump efficiency. In this study, we measured the thermal stabilities and the emission cross‐sections for Er 3+ : 4 I 13/2 → 4 I 15/2 transition in this tellurite glass system. We also determined the Judd‐Ofelt parameters and calculated the radiative transition rates and the multiphonon relaxation rates in this glass system. The 15 mol% substitution of B 2 O 3 for TeO 2 in the Er 3+ ‐doped 75TeO 2 ‐20ZnO‐5K 2 O glass raised the multiphonon relaxation rate for 4 I 11/2 → 4 I 13/2 transition from 4960 s −1 to 24700 s −1 , but shortened the lifetime of the 4 I 13/2 level by 14 % and reduced the emission cross‐section for the 4 I 13/2 → 4 I 15/2 transition by 11%. The 15 mol% GeO 2 substitution in the same glass system also reduced the emission cross‐section but increased the lifetime by 7%. However, the multiphonon relaxation rate for 4 I 11/2 → 4 I 13/2 transition was raised merely by 1000 s −1 . Therefore, a mixed substitution of B 2 O 3 and GeO 2 for TeO 2 was concluded to be suitable for the 980 nm pump efficiency and the fluorescence efficiency of 4 I 13/2 → 4 I 15/2 transition in Er 3+ ‐doped tellurite glasses.