Amplified spontaneous emission

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.

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Origins and problems

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 limits the maximum gain that can be achieved in the gain medium. ASE creates serious problems in any laser with high gain and/or large size. In this case, a mechanism to absorb or extract the incoherant ASE must be provided, otherwise the excitation of the gain medium will be depleted by the incoherent ASE rather than by the desired coherent laser radiation. ASE is especially problematic in lasers with short and wide optical cavities, such as disk lasers (active mirrors). ^[1].

ASE in disk lasers: Controversy

According to some publications, at the power scaling of disk laser]s, the round-trip gain should be reduced ^[2], which means hardening of requirement on the background loss. Other colleagues think, the existing disk lasers work far from such a limit, and the power scaling can be achieved without modification of existing laser materials ^[3].

References

1. ^ D.Kouznetsov; J.F.Bisson, K.Takaichi, K.Ueda (2005). "Single-mode solid-state laser with short wide unstable cavity". JOSAB 22 (8): 1605-1619.
2. ^ D. Kouznetsov; J.F. Bisson, J. Dong, and K. Ueda (2006). "Surface loss limit of the power scaling of a thin-disk laser". JOSAB 23 (6): 1074-1082. Retrieved on 2007-01-26.; [1]
3. ^ A. Giesen; H. Hügel, A. Voss, K. Wittig, U. Brauch and H. Opower (1994). "Scalable concept for diode-pumped high-power solid-state lasers". Applied Physics B 58 (5): 365–372.

See also

• maser
• disk laser