Gain cross section measurements on the 2.8 µm laser transition of Er3+ doped BaY2F8 single crystal

The ~2.8 µm laser transition of Er3+ ions is interesting for medical application. The transition takes place between the two excited states 4I11/2 and 4I13/2. In the fluoride crystals this emission is efficient due to low nonradiative processes between these two levels. The Er3+:BaY2F8 [1] is one of the most interesting crystals for 2.8 µm emission because the lifetime ratio between 4I11/2 and 4I13/2 is closed to one and the phonon energy is low compared to LiYF4. Some strong excitation transfer processes make difficult the prediction of the efficiency by a population rate equations model. It’s important to know the gain cross section and population inversion rate to predict the laser properties.