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Proceedings Paper

Intensity Fluctuations Resulting From The Propagation Of Partially Coherent Beam Waves In The Turbulent Atmosphere
Author(s): J. Carl Leader
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Paper Abstract

The random phase-front resulting from the reflection of a laser beam from a rough surface produces the spatially random optical intensity fluctuations commonly referred to as speckle patterns. If the rough surface moves with respect to the laser beam (so that independent samples of the rough surface are illuminated) or if the scattered beam propagates through the wind-blown turbulent atmosphere, a fixed detector observes a time-fluctuating optical field that can be analyzed using the techniques of coherence theory. Because most experiments measure the optical intensity, the extended Rayleigh-Sommerfield technique (developed earlier) is employed to investigate intensity fluctuations resulting from atmospheric propagation of a curved, random, beam-amplitude wave front that results from laser-beam reflection from a curved rough-surface. The normalized intensity covariance is calculated by extending the recently developed intensity fluctuation analysis to curved phase-fronts. Calculations show that the normalized intensity variance is minimized when the field point is at the focus of the source and there is no turbulence (unsaturated speckle propagation), whereas a maximum variance results when the source is perfectly co-herent (focused laser beam) and the atmosphere is turbulent. Intermediate results are obtained when the source is partially coherent and propagates in the turbulent atmosphere. Because a laser beam becomes partially coherent as it propagates through atmospheric turbulence, the method of smooth perturbations and the extended Huggens-Fresnel technique fail to predict observed beam characteristics in strong turbulence. Observed saturation phenomena are predicted by calculating the coherence properties of the beam at intervals in the propagation path.

Paper Details

Date Published: 25 October 1979
PDF: 15 pages
Proc. SPIE 0194, Applications of Optical Coherence, (25 October 1979); doi: 10.1117/12.957913
Show Author Affiliations
J. Carl Leader, McDonnell Douglas Research Laboratories (United States)

Published in SPIE Proceedings Vol. 0194:
Applications of Optical Coherence
William H. Carter, Editor(s)

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