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(11)¡¡Generation and properties of laser speckle with long correlation tails
¡¡¡¡¡¡¡¡Saratov Fall Meeting 2001: Coherent Optics of Ordered and Random Media II, ed. D. A. Zimnyakov,
¡¡¡¡¡¡¡¡Proceedings of SPIE, Vol.4705, pp.95-106, 2002-4
¡¡Speckle patterns produced by scattering in random media are sometimes employed as tools for optical measurements and information processing. In those applications of speckles, spatial and temporal correlation properties play sometimes fundamental roles. Therefore, design and control of correlation properties in the scattered fields are an attractive and important subject. From this viewpoint, two types of speckle patterns having extraordinary spatial correlations are reviewed and discussed in this article. The first type of scattered fields is nondiffracting, or propagation-invariant speckles. This type of waves have Bessel-type long tails in transverse intensity correlations and extremely long correlation in the propagation direction. Two schemes for generating nondiffracting speckles by means of an annular aperture and an axicon lens are described. Relations to general nondiffracting beams are also discussed briefly. The second type of waves having long-range correlations is fractal speckles, which have negative power-law intensity correlations in lateral and longitudinal directions. Results of computer simulations are shown for fractal speckles with wide range of a parameter D governing the spatial extent of correlations.
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