Sound amplification by stimulated emission of radiation vector in the second proposed scheme, is supposed to be determined by magnitude of in-plane magnetic field. Therefore, such kind of SASER is tunable (i.e. its wavelength of operation can be altered in a controlled manner). Common semiconductor lasers can be realised only in direct gap semiconductors. The reasoning behind that is that a pair of electron and hole near minima of their bands in an indirect gap semiconductor can recombine only with production of a phonon and a photon, due to energy and momentum conservation laws. This kind of process is weak in comparison with electron-hole recombination in a
Sound amplification by stimulated emission of radiation leads to the appearance of an additional quasi-periodic wave. This wave is coupled with the spatial variation of the bubble density under the action of radiation pressure forces. Hence, the wave amplitude and the bubble density vary slowly compared with the period of the oscillations. In the theoretical scheme where the usage of resonators is essential, the SASER radiation passes through the resonator walls, which are perpendicular to the direction of propagation of the pump wave. According to an example of an electrically pumped SASER, the active medium is confined between two planes, which are defined by the solid walls