Amplified spontaneous emission
- 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.
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 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). [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] .]ASE in disk lasers: Controversy
According to some publications, at the
power scaling of disk lasers, the round-trip gain should be reduced [cite journal| author=D. Kouznetsov|coauthors= J.F. Bisson, J. Dong, and K. Ueda| title=Surface loss limit of the power scaling of a thin-disk laser| journal=JOSAB| volume=23| issue=6| pages=1074–1082| year=2006| url=http://josab.osa.org/abstract.cfm?id=90157| accessdate=2007-01-26| doi=10.1364/JOSAB.23.001074; [http://www.ils.uec.ac.jp/~dima/disk.pdf] ] , 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 [cite journal| author=A. Giesen| coauthors=H. Hügel, A. Voss, K. Wittig, U. Brauch and H. Opower| title=Scalable concept for diode-pumped high-power solid-state lasers| year=1994
url=http://www.springerlink.com/content/n7350870q8q57324/?p=c874af0585094717b13bb41e3fc548da&pi=0
journal=Applied Physics B|volume=58| issue=5| pages=365–372| doi=10.1007/BF01081875] .
References
ee also
*maser
*disk laser
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