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 dispersion law away from the radiation zone. The importance of this, lies on the fact that electric and in-plane magnetic fields normal to coupled quantum wells, can control the dispersion of indirect exciton. Normal electric field is needed for tuning the transition: direct exciton --> indirect exciton + phonon into resonance and its magnitude can form a linear function with the magnitude of in-plane magnetic field. We note that the mathematical analysis of this scheme considers of longitudinal acoustic (LA) phonons instead of transverse acoustic (TA) phonons. This aims to more simple numerical estimations. Generally, the preference in transverse acoustic