Temperature effects in nonequilibrium phonon decay

We have investigated the spectral and temporal dynamics associated with the interaction between monochromatic and thermal phonon distributions in YAG:Pr3+. Using defect-induced one-phonon absorption to generate a monochromatic phonon distribution at 43.3 cm-1, we measure a T-3 dependence of the monochromatic phonon lifetime in the temperature range 9 to 25 K. We observe the evolution of additional broadband phonon distributions which do not occur at low temperatures.