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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 44, Iss. 14 — May. 10, 2005
  • pp: 2805–2817

Near-field nonuniformities in angularly multiplexed KrF fusion lasers with induced spatial incoherence

Robert H. Lehmberg and Yung Chan  »View Author Affiliations


Applied Optics, Vol. 44, Issue 14, pp. 2805-2817 (2005)
http://dx.doi.org/10.1364/AO.44.002805


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Abstract

Induced spatial incoherence (ISI) has been proposed for KrF laser drivers to achieve the high degree of spatial beam uniformity required for direct-drive inertial confinement fusion. Although ISI provides ultrasmooth illumination at the far field of the laser, where the target is located, it can still allow the beams in the quasi-near field to develop a time-averaged spatial structure. This speckle, which arises primarily from random-phase aberration, builds up as the laser beams propagate away from the pupil plane located at the final amplifier stage; it is distinct from any structure imposed by gain nonuniformities in the amplifiers. Because of the spatial incoherence, the speckle is significantly smaller than that experienced by coherent beams. Nevertheless, it remains a damage issue, especially for the long beam delay paths required in angularly multiplexed KrF lasers. We develop a novel algorithm for calculating the time-integrated intensities; compare simulations and measurements of the near-field speckle in the Nike KrF laser; and explore options, such as aberration reduction and optical relaying, for controlling the problem in future angularly multiplexed KrF drivers.

© 2005 Optical Society of America

OCIS Codes
(030.6140) Coherence and statistical optics : Speckle
(030.6600) Coherence and statistical optics : Statistical optics
(070.2590) Fourier optics and signal processing : ABCD transforms
(140.2180) Lasers and laser optics : Excimer lasers
(350.2660) Other areas of optics : Fusion
(350.5500) Other areas of optics : Propagation

Citation
Robert H. Lehmberg and Yung Chan, "Near-field nonuniformities in angularly multiplexed KrF fusion lasers with induced spatial incoherence," Appl. Opt. 44, 2805-2817 (2005)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-44-14-2805


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