Energy transfer processes in Yb3+ and Tm3+ ion-doped fluoride crystals

Energy transfer processes from Yb3+ to Tm3+ ions have been investigated in various fluoride microcrystals to examine the application limit of a simple rate equation model and to obtain methods for characterizing the host mate rials as to energy transfer. It has been shown that the energy transfer coe fficients from donor Yb3+ to acceptor Tm3+ ions differ by nearly one order of magnitude even for fluoride lattices that have similar luminescence char acteristics. The energy transfer coefficients increase monotonically with Y b3+ concentration at low Yb3+ concentrations, while they take nearly consta nt values at high Yb3+ concentrations. The present experimental results wer e compared with computer simulation results as well as related analyses. It is shown that the apparently complicated behaviors are consistently explai ned by a microscopic model. As an example of the application of the present results, the optimization of the infrared emission of Tm3+ ions is shown. (C) 1999 American Institute of Physics. [S0021-8979(99)01508-X].