Stimulated emission is a process in which an incoming photon causes an excited atom or molecule to release its energy in the form of another photon. This emitted photon has the same energy, phase, and direction as the incoming one, leading to a coherent light output. This principle is fundamental in the operation of devices like lasers. In a laser, a medium is energized to create a population of excited atoms. When these atoms undergo stimulated emission, they produce a cascade of photons, amplifying the light. This results in a highly focused and intense beam of light, which is used in various applications, from medical treatments to telecommunications.