Physical review. B, Condensed matter
Laserlike self-excitation of phonons by an inhomogeneously broadened three-level system
Wolfgang Grill, L. Hirschbiegel
Abstract
An inhomogeneously broadened three-level electronic system related to impurity ions embedded in a crystal with anisotropic phonon modes is considered. It is shown that such a system can sustain laserlike self-excitation under a steady-state condition, depending on the crystal properties. The anisotropy of the phonons is represented by two sets of modes which are distinguished by their lifetimes. Laserlike self-excitation has been shown to be impossible for isotropic systems. This and the influence of crystal properties on the self-excitation in anisotropic systems are discussed.