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Coherent addition

Coherent addition (or coherent combining) of lasers is a way to increase the output power and brightness of single-transversal mode laser. Usually, it applies to fiber lasers. As the ability of pumping and/or cooling of a single laser is saturated, several similar lasers can be forced to oscillate in phase with common coupler. The coherent addition was considered as a way of power scaling of Raman lasers.[1]


Limits of coherent addition

The addition of lasers reduces the number of longitudinal modes in the output beam; the more lasers are combined, the smaller is number of longitudinal modes in the output. The number of output modes reduces exponentially with number of lasers combined. Of order of 8 lasers can be combined in such a way.[2] The future increase of number of combined lasers requires the exponential growth of the spectral bandwidth of gain and/or length of partial lasers. The combinaiton of more than 10 lasers in such a way should be difficult if at all.


  1. ^ A. Shirakawa, T. Saitou, T. Sekiguchi and K. Ueda: "Coherent addition of fiber lasers by use of a fiber coupler" Optics Express 10 (2002) 1167–1172.
  2. ^ D. Kouznetsov, J.F. Bisson. A. Shirakawa, K.Ueda "Limits of Coherent Addition of Lasers: Simple Estimate" Optical Review Vol. 12, No. 6, 445–­447 (2005). (Also [1].)
  • A. E. Siegman: "Resonant modes of linearly coupled multiple fiber laser structures", Stanford University homepage (2004).
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Coherent_addition". A list of authors is available in Wikipedia.
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