Spontaneous emission luminescent. And there are different forms of luminescence depending on how excited atoms are produced (electroluminescence, chemiluminescence etc.). If the excitation is affected by the absorption of radiation the spontaneous emission is called fluorescence. Sometimes molecules have a metastable level and continue to fluoresce long after the exciting radiation is turned off; this is called phosphorescence. Figurines that glow in the dark are phosphorescent. Lasers start via spontaneous emission, then during continuous operation work by stimulated emission. Spontaneous emission cannot be explained by classical electromagnetic theory and is fundamentally a quantum process. The first person to derive the rate of
Sound amplification by stimulated emission of radiation optics. Basic understanding of the SASER development requires the evaluation of some proposed examples of SASER devices and SASER theoretical schemes. In this proposed theoretical scheme, the active medium is a liquid dielectric (e.g. ordinary distilled water) in which dispersed particles are uniformly distributed. Means of electrolysis cause gas bubbles that serve as the dispersed particles. A pumped wave excited in the active medium produces a periodic variation of the volumes of the dispersed particles (gas bubbles). Since, the initial spatial distribution of the particles is uniform, the waves emitted by the particles are added with different phases and give