Improvement of 4I11/2 → 4I13/2 transition rate and thermal stabilities in Er3+-doped TeO2-B2O3(GeO2)-ZnO-K2O glasses

Spectroscopic and thermal analysis indicates that tellurite glasses doped with B2O3 and GeO2 are promising candidate host materials for wide-band erbium doped fiber amplifier (EDFA) with a high 980 run pump efficiency. In this study, we measured the thermal stabilities and the emission cross- sections for Er3+ : I-4(13/2) --> I-4(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 B2O3 for TeO2 in the Et3+-doped 75TeO(2)-20ZnO-5K(2)O glass raised the multiphonon relaxation rate for I-4(11/2) --> I-4(13/2) transition from 4960 s(-1) to 24700 s(-1), but shortened the lifetime of the I-4(13/2) level by 14 % and reduced the emission cross-section for the I-4(13/2) --> I-4(15/2), transition by 11%. The 15 mol% GeO2 substitution in the same glass system also reduced the emission cross-section but increased the lifetime by 7%. However, the multiphonon relaxation rate for I-4(11/2) --> I-4(13/2) transition was raised merely by 1000 s(-1). Therefore, a mixed substitution of B2O3 and GeO2 for TeO2 was concluded to be suitable for the 980 nm pump efficiency and the fluorescence efficiency of I-4(13/2) --> I-4(15/2) transition in Er3+-doped tellurite glasses.