The spectroscopy of mid-infrared (2.9 μm) fluorescence and energy transfer in Dy3+-doped tellurite glasses

The decay processes relating to the potential 6H13/2 - 6H15/2 laser transition for 3-µm emission in singly Dy3+-doped tellurite (TZNF and TZN) glasses have been investigated in detail using time-resolved fluorescence spectroscopy. The selective laser excitation of the 6F5/2 and 6H9/2, 6F11/2 energy levels at 805 nm and 1300 nm, respectively have established that the decay processes of the lowest excited level (i.e., 6H13/2) entirely favors multiphonon emission in a tellurite glass host. Detailed investigation of the 6H13/2 luminescence decay characteristic revealed that two decay constants are involved in the TZNF glass composition; approximately 90% of the decay has a time constant (τ1) of 19.6 μs. The rest of the centers decay with a time constant τ2 = 112 μs due to the Dy3+ - fluorine bonds that are possibly present in the TZNF glass matrix. Slight quenching of τ1 for Dy3+ concentration increases to 2 mol% may indicate energy transfer to OH- molecules in the TZNF glass despite the low OH content, [α(OH-) ~0.04 cm-1]; further decrease of τ1 (to 9.7 μs) was measured in TZN glass matrix which is commensurate with the higher OH density (α = 0.15 cm-1).