LASER TIME-RESOLVED SPECTROSCOPY STUDIES OF HOST-SENSITIZED ENERGY-TRANSFER IN BI4GE3O12-ER3+ CRYSTALS

Laser-excited, time-resolved spectroscopy techniques were used to investigate host-sensitized energy transfer in bismuth germanate crystals doped with erbium. The transfer characteristics at room temperature are consistent with a thermally-activated migration process. The transfer rate decreases exponentially as temperature is lowered and reaches a minimum near 75 K. An increase in the transfer rate is observed as temperature is lowered further and the transfer characteristics become consistent with a single step dipole-dipole interaction process. This low temperature behavior is correlated with the observations in undoped bismuth germanate at these temperatures of a significant shift to lower energy of the fluorescence peak position and a significant increase in the fluorescence lifetime. A trapped exciton model is proposed to explain these results. © 1979.