Nonradiative energy-transfer processes in Cd1−xMnxF2 crystals

Abstract

The absorption and fluorescence spectra and fluorescence decay kinetics of Cd_1−x Mn_xF₂ 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.