Spectroscopic properties of ～2 μm emissions of Tm3+-doped germanate-tellurite glasses

Tm2O3-doped 40GeO2-35TeO2-15PbO-5Al2O3-2.5CaO-2.5SrO glasses with different Tm3+ ion concentrations are fabricated by conventional melt-quenching method. From the measurements of thermal properties it follows that the glass transition temperature is 446 ℃ and crystallization peak does not exist. The maxmium phonon energy of the host is ~ 750 cm-1. The Judd-Ofelt strength parameter Ωt (t = 2, 4, 6), the radiative transition probalities, the branching ratios and the radiative lifetime are calculated according to Judd-Ofelt theory. The emission spectra of Tm3+ doped glasses with different Tm2O3 concentrations are measured under the excitation by an 808 nm diode laser. The result shows that the emission intensity at ~ 1.8 μm reaches a maximal value when the Tm2O3-doping concentration is 1 mol% and then it decreases with the further increase of Tm2O3-doping concentration. The emission cross section of 3F4 → 3H6 is calculated based on the McCumber theory. The peak emission cross-section is 6.5 × 10-21 cm2. The non-radiative transition rate of 3F4 caused by OH is calculated quantitatively by rate equation. The results indicate that the germanate-tellurite glass is a new candidate for mid-infrared laser application.