Physical review. B, Condensed matter
Phonon enhancement and saturation in a three-level system
Benjamin Fain
Abstract
A model consisting of a distribution of three-level systems (defects or ionic impurities) in a lattice characterized by a given phonon spectrum is considered in detail. Equations determining the temporal behavior of such a system in an electromagnetic field are analyzed. A steady-state solution describing three-level saturation in the system is achieved. The possibility of the stimulated emission of phonons is considered. It is shown that laserlike self-excitation of phonons cannot be realized, though phonon flux enhancement may be achieved provided certain conditions are fulfilled.