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 is possible. In a two level system, the particles have only two available energy levels, separated by some energy difference: "ΔΕ = E - E = hv" where "ν" is the frequency of the associated electromagnetic wave of the photon emitted and "h" is the Planck constant. Also note: "E" > "E". These two levels are the excited (upper) and ground (lower) states. When a particle in the upper state interacts with a photon matching the energy separation of the levels, the particle may decay, emitting another photon with the same phase and frequency as the incident photon. Therefore, by