Population inversion atoms in the ground and excited states are equal, the rate of stimulated emission is equal to the rate of absorption for a given radiation density. The critical detail of stimulated emission is that the induced photon has the same frequency and phase as the incident photon. In other words, the two photons are coherent. It is this property that allows optical amplification, and the production of a laser system. During the operation of a laser, all three light-matter interactions described above are taking place. Initially, atoms are energized from the ground state to the excited state by a process
Sound amplification by stimulated emission of radiation of the resonator. The radiation then, propagates along an axis parallel to the plane defined by the two resonator walls. The static electric field acting on the liquid with gas bubbles results in the deformation of dielectrics and therefore leads to a change in the volumes of the particles. We note that, the electromagnetic waves in the medium propagate with a velocity much greater than the velocity of sound in the same medium. This results to the assumption that the effective pump wave acting on the bubbles does not depend on the spatial coordinates. The pressure of a wave pump