Resonant excited state absorption and relaxation mechanisms in Tb3+-doped calcium aluminosilicate glasses: an investigation by thermal mirror spectroscopy

Resonant excited state absorption (ESA) and relaxation processes in Tb3 -doped aluminosilicate glasses are quantitatively evaluated. A model describing the excitation steps and upconversion emission is developed and applied to interpret the results from laser-induced surface deformation using thermal mirror spectroscopy. The fluorescence quantum efficiency of level 5D4 was found to be close to unity and concentration independent while, for the level 5D3, it decreases with Tb3 concentration. Emission spectroscopy measurements supported these results. ESA cross sections are found to be more than three orders of magnitude higher than the ground state absorption cross section