Abstract
The stepwise conversion of infrared () radiation to near infrared (0.81 μ) and visible (0.475 μ) light in Y sensitized with and activated with has been studied in detail. The lifetimes and fluorescence intensities of the important manifolds (, , , and ), as well as the Yb-to-Tm transfer probability coefficients for the three steps of the process, have been measured as functions of concentration. A saturation effect previously observed in the Tm emission versus infrared excitation intensity has been shown to result from the rate of depopulation of by the second Yb-to-Tm transfer exceeding the decay rate. This was used to determine the second transfer probability coefficient. The first transfer probability coefficient was found to be 1.2× independent of Tm concentration and for Yb concentration of the order of 10 at.% and greater. The second transfer probability coefficient was found to be approximately for Yb concentrations of 25 at.% and greater. The third transfer probability coefficient was found to be 2.7× . The dependence on Yb concentration of the relative efficiency of conversion to 0.475-μ light agrees well with the values calculated from a rate-equation model using the measured lifetimes and transfer probability coefficients.
- Received 5 October 1970
DOI:https://doi.org/10.1103/PhysRevB.3.2698
©1971 American Physical Society