Fluorescence quantum efficiency measurements of excitation and nonradiative deexcitation processes of rare earth 4f-states in chalcogenide glasses

Thermal lens spectroscopic measurements were performed to quantitatively determine the fluorescence quantum efficiency (eta) of different luminescence mechanisms in Nd3+ chalcogenide glasses. Low energy (<1.7 eV) direct resonant pumping at Nd3+ infrared lines resulted in eta ~1. High energy (~2.4 eV) indirect excitation via energy transfer (ET) from glass conduction band to Nd3+ 4f states, resulted in eta = ~0.4 (ET probability ~40%). A minimum eta ~0.2 was obtained for intermediate excitation energies (~2.2 eV) and attributed to back ET from the Nd3+ 4f state to the glass host