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Proceedings Paper

Propagation of combined laser beams through atmospheric turbulence (Conference Presentation)

Paper Abstract

To achieve the power levels necessary for directed energy applications with fiber or slab lasers, it is necessary to combine multiple lasers into a single beam director. Here we compare the performance of incoherent and coherent beam combining strategies and address three important issues that should be considered before a beam combining architecture is implemented. First, we consider the difficulty in phase locking high-power fiber and slab lasers. The large linewidths of high-power fiber and slab lasers induce random phase fluctuations occurring on sub-nanosecond time scales. To coherently combine these high-power lasers can involve rapid and precise phase control to compensate for these fluctuations. Even with a master oscillator - multiple power amplifier system, the coherence length of the beams to be combined is very short necessitating continuous precise control of optical path lengths. Second, we consider the dephasing effects of atmospheric turbulence. We find that in moderate to strong turbulence conditions and kilometer propagation distances, coherent combining at the transmitter plane has negligible impact on the energy delivered to a target. Finally, we consider the multifaceted task of coherent combining at the target plane. This is effectively an adaptive optics situation in which the distortions caused by atmospheric turbulence are partially compensated for.

Paper Details

Date Published: 7 December 2016
PDF: 1 pages
Proc. SPIE 9979, Laser Communication and Propagation through the Atmosphere and Oceans V, 99790N (7 December 2016); doi: 10.1117/12.2239140
Show Author Affiliations
William Nelson, Univ. of Maryland, College Park (United States)
Chensheng Wu, Univ. of Maryland, College Park (United States)
Phillip Sprangle, Univ. of Maryland, College Park (United States)
U.S. Naval Research Lab. (United States)
Christopher C. Davis, Univ. of Maryland, College Park (United States)

Published in SPIE Proceedings Vol. 9979:
Laser Communication and Propagation through the Atmosphere and Oceans V
Alexander M. J. van Eijk; Christopher C. Davis; Stephen M. Hammel, Editor(s)

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