Sound amplification by stimulated emission of radiation mechanism into the active medium is the existence of superlattice layers that reflect the phonons back and force them to bounce repeatedly to amplify sound. Therefore, to proceed to an understanding of a SASER design we need to imagine it in analogy with a laser device. In a laser, the active medium is placed between two mirror surfaces (reflectors)of a Fabry–Pérot interferometer. A spontaneously emitted photon inside this interferometer can force excited atoms to decay a photon of same frequency, same momentum, same polarization and same phase. Because the momentum (as a vector) of the photon is nearly parallel to
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