Amplified spontaneous emission: Difference between revisions
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==Origins and problems== |
==Origins and problems== |
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ASE is produced when a [[laser]] gain medium is [[laser pumping|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 incoherent ASE must be provided, otherwise the [[excited state|excitation]] of the [[gain medium]] will be depleted by the incoherent ASE rather than by the desired [[Coherence (physics)|coherent]] laser [[radiation]]. ASE is especially problematic in lasers with short and wide optical cavities, such as [[disk laser]]s (active mirrors).<ref name="uns">{{cite journal| author=D.Kouznetsov| coauthors=J.F.Bisson, K.Takaichi, K.Ueda| title=Single-mode solid-state laser with short wide unstable cavity| url=http://josab.osa.org/abstract.cfm?id=84730| journal=[[JOSAB]]| volume=22| issue=8| pages=1605–1619| year=2005| doi=10.1364/JOSAB.22.001605| bibcode=2005JOSAB..22.1605K}}</ref> |
ASE is produced when a [[laser]] gain medium is [[laser pumping|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 is not coherent, and 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 incoherent ASE must be provided, otherwise the [[excited state|excitation]] of the [[gain medium]] will be depleted by the incoherent ASE rather than by the desired [[Coherence (physics)|coherent]] laser [[radiation]]. ASE is especially problematic in lasers with short and wide optical cavities, such as [[disk laser]]s (active mirrors).<ref name="uns">{{cite journal| author=D.Kouznetsov| coauthors=J.F.Bisson, K.Takaichi, K.Ueda| title=Single-mode solid-state laser with short wide unstable cavity| url=http://josab.osa.org/abstract.cfm?id=84730| journal=[[JOSAB]]| volume=22| issue=8| pages=1605–1619| year=2005| doi=10.1364/JOSAB.22.001605| bibcode=2005JOSAB..22.1605K}}</ref> |
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===ASE in organic dye lasers=== |
===ASE in organic dye lasers=== |
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Revision as of 19:04, 21 February 2015
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. It is inherent in the field of random lasers.
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 is not coherent, and 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 incoherent 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 organic dye lasers
ASE in pulsed organic dye lasers can have very broad spectral characteristics (as much as 40-50 nm wide) and presents, as such, a serious challenge in the design and operation of tunable narrow-linewidth dye lasers. In order to suppress ASE, in favor of pure laser emission, researchers use various approaches including optimized laser cavity designs.[2]
ASE in disk lasers: Controversy
According to some publications, at the power scaling of disk lasers, the round-trip gain should be reduced,[3] which means hardening of requirement on the background loss. Other researchers believe the existing disk lasers work far from such a limit, and the power scaling can be achieved without modification of existing laser materials .[4]
ASE in self healing dye doped polymers
Recently a group at Washington state university observed reversible photodegradation or simply, self healing in organic dyes like Disperse orange 11[5] when doped in polymers. They used amplified spontaneous emission as a probe to study self healing properties.[6]
References
- ^ D.Kouznetsov (2005). "Single-mode solid-state laser with short wide unstable cavity". JOSAB. 22 (8): 1605–1619. Bibcode:2005JOSAB..22.1605K. doi:10.1364/JOSAB.22.001605.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ F. J. Duarte (1990). "Narrow-linewidth pulsed dye laser oscillators". Dye Laser Principles. Boston: Academic Press. pp. 133–183 and 254–259. ISBN 0-12-222700-X.
{{cite book}}: Unknown parameter|editors=ignored (|editor=suggested) (help) - ^ D. Kouznetsov (2006). "Surface loss limit of the power scaling of a thin-disk laser". JOSAB. 23 (6): 1074–1082. Bibcode:2006JOSAB..23.1074K. doi:10.1364/JOSAB.23.001074. Retrieved 2007-01-26.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help); [1] - ^ A. Giesen (1994). "Scalable concept for diode-pumped high-power solid-state lasers". Applied Physics B. 58 (5): 365–372. Bibcode:1994ApPhB..58..365G. doi:10.1007/BF01081875.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&N5=SEARCH_CONCAT_PNO%7CBRAND_KEY&N4=217093%7CSIAL&N25=0&QS=ON&F=SPEC
- ^ Natnael B. Embaye, Shiva K. Ramini, and Mark G. Kuzyk, J. Chem. Phys. 129, 054504 (2008) http://arxiv.org/abs/0808.3346
See also
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