Spectroscopy and frequency upconversion inNd3+-dopedTeO2–TiO2–Nb2O5 glass

Abstract

In this work, we report the optical properties ofNd3+ ions in telluriteglasses (TeO2–TiO2–Nb2O5) fortwo different Nd3+ concentrations. Judd–Ofelt intensity parameters were derived from the absorptionspectrum and used to calculate the radiative lifetime and stimulated emissioncross section of the transition. The non-exponential character of the decays from the4F3/2 level and the reduction of the lifetime even at low temperature asNd3+ concentration increases reveal the presence of nonradiative processes. The time evolution of the decaysfrom the 4F3/2 level is consistent with a dipole–dipole direct energy transfer mechanism. Upconversionprocesses that produce green, orange, and red emissions after infrared excitation in the4F3/2 and 4F5/2 levels have been investigated by using steady-state and time-resolved laser spectroscopy.The characteristics of the excitation spectra together with the temporal behaviour of thedecays from the upconverted luminescence suggest that energy transfer upconversionprocesses are the dominant mechanisms in such emissions.