Vibrational and Electronic Dynamics of Tetravalent Chromium Ions in DielectricCrystals

摘要

The research program demonstrated that the overall nonradiative deexcitation'taking place in impurity-doped laser crystals can be broken down into three distinct steps: generation of local mode population due to transition through electronic bottleneck, energy transfer from local into select phonon modes via local-phonon mode coupling and return of the system to thermal equilibrium via interaction of the active phonons with the phonon bath. The mechanism of the nonradiative decay is investigated for each step using three experimental techniques: resonance Raman scattering for the identification of Cr sub 4+ local modes, and up-converted hot luminescence and time resolved Raman scattering for the identification of the phonons involved in the nonradiative decay. The dynamics of the phonon modes involved in the nonradiative relaxation was analyzed using a newly developed theoretical model which provided characteristic relaxation time parameters. This work provided the first step in understanding how to alter and control the flow of nonradiative energy.