Spectroscopy and orange-blue frequency upconversion in Pr3+-doped GeO2-PbO-Nb2O5glass

Abstract

The visible luminescence of Pr³⁺-doped lead-germanate glass of composition (in mol%) 60GeO₂-25PbO-15Nb₂O₅ has been investigated for different Pr³⁺ concentrations and temperatures by using steady-state and time-resolved laser spectroscopy. The fluorescence from the ¹D₂ level shows a strong concentration quenching for Pr³⁺ concentrations higher than 0.1 mol%. The time evolution of the decays from the ¹D₂ level and the concentration dependence of the effective decay rates are consistent with a dipole-dipole quenching process in the framework of a diffusion-limited regime. Anti-Stokes emission from the ³P₀ level following excitation of the ¹D₂ state has been observed for the samples doped with 0.1, 0.5, 1, and 2 mol% of Pr³⁺. The temporal behaviour of the upconverted emission from the ³P₀ level together with its quadratic dependence on the excitation energy and its linear dependence on Pr³⁺ concentration suggest that an excited-state absorption (ESA) is the dominant mechanism for the upconversion process in this glass.