Temperature anomalies of emission spectra of Nd:Yb:La2CaB10O19 single crystals

We have performed experimental investigations of absorption and emission spectra of Nd:Yb:La2CaB10O19 single crystals at different impurity content and temperatures. It was established that intensity of the Nd emission line at 910-930 nm is changed inversely after addition of Yb to the Nd doped crystals. This fact can indicate principal role of the Yb ions in the observed temperature features. Moreover, efficiency of transfer process increases with the temperature's rising. The maximum efficiency is gained for 350 K and afterwards it is diminished. Modification of population occurs among Stark's energy levels. The possible explanations for observed temperature dependences are connected by change of the phonon-assisted relaxation process and emission spectra and the back transfer Nd+3 ← Yb+3 that is thermally activated.