A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.- Laser
An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed.- Optical amplifier
In doped fiber amplifiers and bulk lasers, stimulated emission in the amplifier's gain medium causes amplification of incoming light.- Optical amplifier
However, when a population inversion is present, the rate of stimulated emission exceeds that of absorption, and a net optical amplification can be achieved.- Stimulated emission
Such a gain medium, along with an optical resonator, is at the heart of a laser or maser.- Stimulated emission
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Amplified spontaneous emission (ASE) or superluminescence is light, produced by spontaneous emission, that has been optically amplified by the process of stimulated emission in a gain medium.
ASE is produced when a laser gain medium is pumped to produce a population inversion.