Luminescence properties of Nd³⁺-doped Y₂Te₄O₁₁ microcrystalline powder

In this paper, some spectroscopic properties of Y₂Te₄O₁₁ microcrystalline powders, doped with Nd³⁺ ions are presented. The samples were successfully synthesized by the solid state reaction method. Absorption (300 K) and fluorescence (at 77 and 300 K) spectra as well as the fluorescence decay curves (300 K) of the ⁴F_3/2 state are presented and analyzed. The phenomenological Ω_λ (λ=2, 4, 6) Judd-Ofelt parameters were evaluated in order to determine radiative probabilities (A), branching ratios (β), the radiative lifetime (τ_R) of the ⁴F_3/2 level and the stimulated emission cross-section (σ_em) for the ⁴F_3/2 → ⁴I_J/2 (J=9 and 11) transitions of the Nd³⁺ ion. The fluorescence decay curves were single exponential for 0.01–5.0 at% of Nd³⁺ and became evidently non-exponential for higher Nd³⁺ ion concentration. With increasing activator concentration from 0.01 to 10.0 at%, the experimental lifetime of the emitting level decreases from 95 to 33 μs. The non-exponential fluorescence decay curve has been fitted by the Yokota-Tanimoto model, indicating that the energy migration process via a diffusion limited relaxation, plays a important role in the depopulation of the ⁴F_3/2 level of Nd³⁺ ions doped in the Y₂Te₄O₁₁ microcrystalline powder. The calculated absorption value (1.135×10^–19 cm² at 807.5 nm) of the ⁴I_9/2 → ⁴F_5/2 transition as well as the value of the stimulated emission cross-section (1.196×10^–19 cm² at 1063.5 nm) for that of ⁴F_3/2 → ⁴I_11/2 were compared with the corresponding values of other laser hosts. For the first time a very high σ_em value of the ⁴F_3/2 → ⁴I_11/2 transition for TeO₂-based compounds, has been observed. From the presented spectroscopic properties follows that the Nd³⁺:Y₂Te₄O₁₁ powder is a potential candidate for a random laser host, operating at 1.06 μm.