Amplified spontaneous 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. Feedback of the ASE by the laser's optical cavity may produce laser operation if the lasing threshold is reached. Excess ASE is an unwanted effect in lasers, since it disipates some of the laser's power. In optical amplifiers, ASE limits the achievable gain of the amplifier and increases its noise level.
Devices which produce ASE are called superluminescent sources or superluminescent lasers. ASE sources produce light that has a wide bandwidth, low temporal coherence, but high spatial coherence.
See also
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