Sound amplification by stimulated emission of radiation this scheme with a rather moderate pumping rate can hold against the fact that excitons in coupled quantum wells have low dimensionality in comparison to phonons. Hence, phonons not confined in the coupled quantum well are considered. An example is longitudinal optical (LO) phonons that are in AlGaAs/GaAs heterostructure and thus, phonons presented in this proposed system are three-dimensional. Differences in dimensionalities of phonons and excitons cause upper level to transform into many states of phonon field. By applying this information to specific equations we can conclude to a desired result. There is no additional requirement for the laser pumping
Sound amplification by stimulated emission of radiation of a coherent amplification of THz sound. The THz stimulated phonon induced transitions between the electron superlattice states lead to this coherent amplification while processing a population inversion. An essential step towards coherent generation ("sasing") of THz sound and other active hypersound devices has been provided by this achievement of THz sound amplification. Generally, in a device where the threshold for "sasing" is achieved, the technique described by this proposed scheme could be used to measure the coherence time of the emitted hypersound. Sound amplification by stimulated emission of radiation Sound amplification by stimulated emission of radiation (SASER) refers to