Analyses and applications of singular intensity variations in Gaussian scattering fields of laser light

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Recently, random fields with singular properties were found in the framework of Gaussian speckles. The present study aims at analyzing statistical properties and generation conditions of such random fields through theoretical, experimental and simulation approaches.1. Generating mechanism of structured specklesStructured speckles (clustered speckles) are found to appear when a diffuser is illuminated by a thin ring-slit aperture. An isotropy of the speckle clustering was shown to be due to circular symmetry of the ring slit. An origin of speckle clustering was shown by means of computer simulations. Developing process of partially-developed clustered speckles are revealed experimentally by using small-roughness diffusers.2. Axially long spatial correlationWith relation to properties of a non-diffracting beam, it was shown theoretically that the clustered speckles produced by the ring-slit illumination have very long spatial correlations in the axial direction. The results were verified by experiments.3. Generation of fractal specklesIt was shown experimentally that a double scattering process using a random fractal diffuser and an ordinary diffuser can produce speckle intensity distributions with a fractal property in a Fourier transform plane of the second diffuser. This verified a theoretical prediction given previously. A 3D correlation properties of the speckles were also examined.4. Fractal speckles in Fresnel and image regionsIt was shown that speckle intensity distributions with fractal properties can also be generated in the Fresnel diffraction regions and in the image plane of the ordinary diffuser by using suitable configurations.