Sound amplification by stimulated emission of radiation a mathematical calculation of the starting conditions. Bubbles with resonance frequencies close to the pump frequency make the main contribution to the gain of the useful mode. In contrast, the determination of the starting pressure in ordinary lasers is independent from the number of radiators. The useful mode grows with the number of particles but sound absorption increases at the same time. Both these factors neutralize each other. Bubbles play the main role in the energy dispersion in a SASER. A relevant suggested scheme of sound amplification by stimulated emission of radiation using gas bubbles as the active medium was
Sound amplification by stimulated emission of radiation short-wavelength (in the terahertz range) phonons are produced. Since the electrons are confined to the quantum wells existing within the lattice, the transmission of their energy depends upon the phonons they generate. As these phonons strike other layers in the lattice, they excite electrons, which produce further phonons, which go on to excite more electrons, and so on. Eventually, a very narrow beam of high-frequency ultrasound exits the device. Semiconductor superlattices are used as acoustic mirrors. These superlattice structures must be in the right size obeying the theory of multilayer distributed Bragg reflector, in similarity with multilayer dielectric mirrors in