Sound amplification by stimulated emission of radiation direct semiconductor. Consequently, the pumping of these transitions has to be very intense so as to obtain a steady laser generation. Hence, the lasing transition with production of only one particle – photon – must be resonant. This means that the lasing transition must be allowed by momentum and energy conservation laws to generate in a steady form. Photons have negligible wave vectors and therefore the band extremes have to be in the same position of the Brillouin zone . On the other hand, for devices such as SASERs, acoustic phonons have a considerable dispersion. According to dynamics, this leads
Sound amplification by stimulated emission of radiation exciton level is lower than the level of indirect exciton because of greater Coulomb interaction. Also, indirect exciton has an electric dipole momentum normal to coupled quantum well and thus a moving indirect exciton has an in-plane magnetic momentum perpendicular to its velocity. Any interactions of its electric dipole with normal electric field, lowers one of indirect exciton sub-levels and in sufficiently strong electric fields the moving indirect exciton becomes the ground excitonic level. Having in mind these procedures, one can select velocity to have an interaction between magnetic dipole and in-plane magnetic field. This displaces the minimum of the