Sound amplification by stimulated emission of radiation method of the pumping keeps the system electro-neutral and the dispersion laws of electrons and holes are assumed to be parabolic and isotropic. Also phonon dispersion law is required to be linear and isotropic too. Since the entire system is electro-neutral, the process of pumping creates electrons and holes with the same rate. A mathematical analysis, leads to an equation for the average number of electron-hole pairs per one phonon mode per unit volume. For a low loss limit, this equation gives us a pumping rate for the SASER that is rather moderate in comparison with usual phonon lasers on
Sound amplification by stimulated emission of radiation an optical cavity, but in a different active medium. An example of an active medium is the superlattice. A superlattice can consist of multiple ultra-thin lattices of two different semiconductors. These two semiconductor materials have different band gaps, and form quantum wells—which are potential wells that confine particles to move in two dimensions instead of three, forcing them to occupy a planar region. In the superlattice, a new set of selection rules is composed that affects the flow-conditions of charges through the structure. When this set-up is excited by a source, the phonons start to multiply while they reflect on