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 2.9 μm emission in single 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 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 remaining centers decay with a time constant τ₂ = 112 μs due to the Dy³⁺ fluorine bonds, which 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).7 page(s