Rare-earth-activated fluoride and tellurite glasses: Optical and spectroscopic properties

In this work we report on spectroscopic properties of Er3+-doped aluminum fluorophosphate glasses of molar composition 29.8AlF3: 3.5 MgF2: 19.8 CaF2: 10.9 SrF2: 12.8 BaF2: 8.4 YF3: 9.8 ZrF4: 4 NaPO3: 1 ErF3 and 30 AlF3: 3.5 MgF2: 20 CaF2: 11 SrF2: 13 BaF2: 8.4 YF3: 10 ZrF4: 4 NaPO3: 0.1 ErF3, and Er3+-doped tellurite glasses of molar composition 75 TeO2: 12 ZnO: 10 Na2O: 2 PbO: 1 Er2O3 and 75 TeO2: 12 ZnO: 10 Na2O: 2 GeO2: 1 Er2O3. Absorption and Stokes luminescence upon visible excitation were measured. Emission in the third telecom window was observed upon excitation at 514.5 nm and the lifetime of the 4I13/2 level was measured. Infrared-to-visible upconversion emission under continuous-wave laser excitation at 976 nm was observed. The upconversion results in a strong green emission and a weaker red emission, whose intensity shows a quadratic dependence on the excitation power, indicating that two photons are involved in the process. Lifetime measurements were performed in order to study the dynamical behavior of the upconversion emission and to clarify the contributions of excited state absorption and energy transfer to the upconversion process.