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Proceedings Paper

Wavefront-based stochastic parallel gradient descent beam control
Author(s): Mikhail S. Belen'kii; Kevin Hughes; Hope Runyeon; Vincent Rye
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Paper Abstract

For a non-cooperative target, a laser beacon is created by illuminating the target with a beacon beam. When a beacon beam propagates though deep turbulence, turbulence spreads the beam. A conventional phase conjugate adaptive optics (AO) system is not efficient in the presence of Beacon Anisoplanatism when the beacon beam spot size at the target includes many isoplanatic patch sizes. We introduce a concept of the wavefront-based stochastic parallel gradient decent (WSPGD) AO system, which uses an off-axis wavefront sensor to provide feedback for the beam control algorithm. This concept is based on the finding that the phase aberrations of laser return from the target contain information about beam spot size at the target, and that correction of a limited number of low-order Zernike modes increases on-axis intensity and power in the bucket at the target. We evaluated the WSPGD AO system performance in simulation for two tactical engagement scenarios in the presence of strong turbulence. We found that that the WSPGD AO system can efficiently compensate the effects of strong turbulence including Beacon Anisoplanatism, even when the beam spot size at the target includes up to 20 isoplanatic patch sizes and the isoplanatic angle is by a factor of 2.6 less than the diffraction limit. The Strehl ratio gain for this scenario is 1.6 - 2.5, and the maximum Strehl ratio is achieved after 15-20 iterations. A laboratory demonstration performed under a separate program confirmed our theoretical predictions.

Paper Details

Date Published: 27 September 2007
PDF: 14 pages
Proc. SPIE 6711, Advanced Wavefront Control: Methods, Devices, and Applications V, 67110F (27 September 2007); doi: 10.1117/12.732692
Show Author Affiliations
Mikhail S. Belen'kii, Trex Enterprises Corp. (United States)
Kevin Hughes, Trex Enterprises Corp. (United States)
Hope Runyeon, Trex Enterprises Corp. (United States)
Vincent Rye, Trex Enterprises Corp. (United States)

Published in SPIE Proceedings Vol. 6711:
Advanced Wavefront Control: Methods, Devices, and Applications V
Richard A. Carreras; John D. Gonglewski; Troy A. Rhoadarmer, Editor(s)

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