Scintillation Of Initially Convergent Gaussian Beams In The Vicinity Of The Geometric Focus

    Authors

    W. B. Miller; J. C. Ricklin;L. C. Andrews

    Comments

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    Abbreviated Journal Title

    Appl. Optics

    Keywords

    Turbulent; Optics

    Abstract

    As an initially convergent Gaussian beam enters the vicinity of the geometric focus, weak fluctuation theory predicts a drop in the longitudinal component of the log-irradiance variance and an increase in the radial component off the beam center. The phenomenon intensifies as the beam nears the geometric focus, also with decreasing magnitude of the focusing parameter. Precisely at the geometric focus, first-order weak fluctuation theory further predicts that as the initial beam size continues to increase, the longitudinal component of the log-irradiance variance decreases toward zero, while the radial component increases without bound. This eventually entails a rapid change in scintillation across the beam surface that has yet to be verified experimentally, to our knowledge. We demonstrate that when diffraction like effects produced by optical turbulence are introduced, predicted log-irradiance variance exhibits such extremes in behavior only in the case of weak turbulence. Also, at the exact geometric focus, scintillation does not vanish with increasing initial beam size but achieves a value determined by and growing with turbulence strength and nearly independent of initial beam size. The radial component of log-irradiance quickly loses significance as turbulence strength increases. In fact, general extremal behavior of the log-irradiance variance in the vicinity of the geometric focus is drastically curtailed. Differences across the diffractive beam surface become small and exhibit only a modest dependence on the initial beam size. (C) 1995 Optical Society of America

    Journal Title

    Applied Optics

    Volume

    34

    Issue/Number

    30

    Publication Date

    1-16-1995

    Document Type

    Article

    Language

    English

    First Page

    7066

    Last Page

    7073

    WOS Identifier

    WOS:A1995RZ26800033

    ISSN

    0003-6935

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