Stimulated emission occurs when an already excited atom or molecule interacts with a passing photon, causing it to emit another photon with the same frequency, phase, and direction as the incident photon.
A device that produces an intense, coherent, and monochromatic beam of light through the process of stimulated emission.
Population Inversion: The condition in which more atoms or molecules are in an excited state than in a lower energy state, necessary for stimulated emission to occur.
Absorption Spectrum: The range of wavelengths or frequencies of electromagnetic radiation absorbed by a substance.