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 (I-4(11/2)) in an Er3+(45 at. %):YAlO3 crystal under intense pump in the S-4(3/2) level is performed. The observed nonexponential I-4(11/2) 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 I-4(13/2) and I-4(11/2) and cross-relaxation from S-4(3/2) and I-4(9/2) provided only a small fraction (beta(2) approximate to 0.11) of the excitation from I-4(11/2) level reaches the terminal laser level, I-4(13/2). The low value of beta(21) and the observed reduction of the fluorescent Lifetime of I-4(11/2) with the increasing erbium doping could be related to the presence of accidental impurities. (C) 1996 American Institute of Physics.