Nonradiative energy-transfer processes in Cd1−xMnxF2 crystals

Abstract

The absorption and fluorescence spectra and fluorescence decay kinetics of Cd1−x MnxF2 crystals with x=0.018, 0.063, 0.084, 0.26 were measured as a function of temperature under argon-ion and nitrogen laser excitation. In addition, laser-induced grating measurements were made as a function of write beam crossing angle for various temperatures between 15 and 50 K. It was found that a characteristic intrashell luminescence comes from two Mn subsystems, one composed of single Mn2+ ions and the second of Mn ion aggregates. Based upon the four-wave-mixing experiment, a relatively strong energy migration was found in each of these subsystems, but with a weak, if any, communication between them. The diffusion coefficients for both subsystems increase as the temperature is raised, and above 50 K strong diffusion erases the light-induced gratings beyond the possibility of detection. The long-lived components of the four-wave-mixing transient signals are associated with the other point defects, either created or photoexcited by the strong laser beams.