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Proceedings Paper

Divergence and Strehl ratios of L-G multimode beams
Author(s): David R. Whitehouse
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Paper Abstract

At present, the quality of a laser beam is defined by the parameter M2 or divergence ratio. It is the ratio of the actual far-field divergence of a beam to that of an ideal TEM00 Gaussian beam with the same size waist. It is important because it provides information on beam size for the design of beam delivery systems and on beam focusability for the design of applications which require a small spot size. This parameter, however, relates to the beam size which contains no information on energy distribution within the beam. By defining an additional parameter called the intensity or Strehl ratio which is related to the on-axis, far-field intensity of the beam, one has further information on the smoothness or sharpness of the beam. From an analysis of multimode beams composed of pure Laguerre-Gaussian (L-G) modes, this paper shows that the divergence ratio and Strehl ratio are independent and concludes that both ratios would be beneficial in specifying the `quality' of a beam. For specific cases, these two ratios uniquely determine the energy distribution of a multimode beam, even though the combination of L-G modes is not unique.

Paper Details

Date Published: 22 April 1993
PDF: 12 pages
Proc. SPIE 1834, Laser Energy Distribution Profiles: Measurement and Applications, (22 April 1993); doi: 10.1117/12.143842
Show Author Affiliations
David R. Whitehouse, Whitehouse Associates (United States)

Published in SPIE Proceedings Vol. 1834:
Laser Energy Distribution Profiles: Measurement and Applications
James M. Darchuk, Editor(s)

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