Effects Of A Modified Spectral Model On The Spatial Coherence Of A Laser-Beam

    Authors

    C. Y. Young;L. C. Andrews

    Comments

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    Abbreviated Journal Title

    Waves Random Media

    Keywords

    Physics, Multidisciplinary

    Abstract

    The influence of a modified (bump) spectrum of refractive index fluctuations on the spatial coherence of an optical wave is studied here and compared with that based on a von Karman spectrum. Analytical expressions are derived for the mutual coherence function (mcF) and wave structure function (WSF) of a lowest-order Gaussian beam wave from which the beam spot size and degree of coherence are deduced. The qualitative behaviour of beam spreading and coherence length is basically the same for both spectral models. Also, when the radius of the Fresnel zone and initial beam radius are of comparable size, the presence of a spectral bump appears to have minimal effect on spatial coherence for all beams. However, the choice of spectral model is important for certain ranges of parameters. In particular, the implied spatial coherence length for a collimated beam based on the modified spectrum is significantly smaller than that based on the von Karman spectrum whenever the Fresnel zone is either much larger or much smaller than the initial beam radius, whereas for a focused beam the predicted coherence length based on the modified spectrum is slightly larger when the Fresnel zone size is much smaller than the initial beam radius.

    Journal Title

    Waves in Random Media

    Volume

    4

    Issue/Number

    3

    Publication Date

    1-1-1995

    Document Type

    Article

    Language

    English

    First Page

    385

    Last Page

    397

    WOS Identifier

    WOS:A1994NZ18700011

    ISSN

    0959-7174

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