Inhomogeneous broadening and energy transfer in KNdP4O12:Pr3+

The nature of the inhomogeneous broadening in Pr 3+ -doped KNdP 4 O 12 crystals is examined by the method of site-selection time-resolved spectroscopy. The presence of Pr 3+ ions in two different crystal-field sites, suggested by the observed splitting of the 3 P 0 state, is confirmed by the selectively excited 3 P 0 to 3 F 4 fluorescence spectra. The process of quenching of the 4 F 3/2 neodymium fluorescence in the presence of Pr 3+ traps is studied using time-resolved fluorescence measurements. At low temperature the time dependence of the Nd 3+ fluorescence intensity in 1% Pr 3+ -doped KNdP 4 O 12 is well described by the Inokuti-Hirayama model with the nearest-neighbour transfer rate of 2*10 5 s -1 . The ion-ion transfer rates are also directly measured for various Nd-Nd and Nd-Pr pair satellite lines. Using these results the shape of the 4 F 3/2 fluorescence decay is predicted in the framework of a discrete host structure model and compared with room temperature data. The process of hole burning at the middle of the Nd excitation profile in KNd 0.9 Pr 0.1 P 4 O 12 is explained by the phonon assisted cooperative interaction between Nd and Pr ions.