Population dynamics of the three-micron emitting level of Er3+ in YAlO3

An analysis of the nonexponential behavior of the kinetics of the initial laser level for three-micron generation (4I11/2) in an Er3+(45 at. %):YAlO3 crystal under intense pump in the 4S3/2 level is performed. The observed nonexponential 4I11/2 decay can be satisfactorily described by the rate equation model which includes energy transfer processes inside the system of erbium ions, such as up-conversion from 4I13/2 and 4I11/2 and cross-relaxation from 4S3/2 and 4I9/2 provided only a small fraction (β21≊0.11) of the excitation from 4I11/2 level reaches the terminal laser level, 4I13/2. The low value of β21 and the observed reduction of the fluorescent lifetime of 4I11/2 with the increasing erbium doping could be related to the presence of accidental impurities.