Ion-ion upconversion excitation of the 4f5d configuration in Pr:Y3Al5O12 -: Experiments and Forster theory-based rate equation model

We observe visible pumping of the ultraviolet 4f5d emission of Pr3+ in Y3Al5O12 by ion-ion upconversion. This process contributes significantly to the 4f5d population, indicating that it should be taken into account (along with excited state absorption) when Pr hosts are evaluated for possible upconversion pumped laser operation in the ultraviolet. In addition, we find that a single, time-independent energy transfer parameter cannot explain the observed 4f5d decay wave forms, but that the familiar Forster theory for range-dependent strength of energy transfer can be adapted to explain the main features of our data. Forster theory leads to a formula which the authors believe can be used to assess the potential for upconversion-based lasing on specific transitions. (C) 1999 American Institute of Physics. [S0021-8979(99)07818-4].