Statistical Properties of Dynamic Multiple Scattering Phenomena of Laser Light

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The aim of the project is to reveal the statistical properties of laser light scattered by highly disordered media in motion and to develop new techniques for extracting information about the structure and motion of multiple scattering objects.(1)Dynamic light scattering from multiple diffusers : The temporal properties of light scattered by a cascade of moving random phase screens were studied theoretically under the Fresnel diffraction approximation. It was shown that the scattered light detected through an imaginig system exhibits some important features which cannot be observed in the light detected in the free-space propagation geometry.(2)Dynamic light scattering from particulate media : Dynamic light scattering from flowing particle suspensions was investigated experimentally, changing the volume density of particles from the single scattering regime to the multiple scattering one. Experiments revealed the intimate relationships between the scattering volume formed inside the sa … More mple and the temporal behavior of scattered light in the multiple scattering regime. In addition, it was found that the sensitivities of the intensity fluctuations of light to diffusive and colletive motions of the particles can be changed by controlling the numerical aperture of the imaging system used for detection.(3)Spectral-correlation measurements of multiply-scattered light : The cross-correlations of scattered light intensities with different wavelengths were measured using concentrated flowing microspheres undergoing Brownian motion. It was shown that the correlation coefficient of intensity fluctuations is mainly dependent both on the scattering cross section of each particle and the number density of the particles. The correlation time measured by the cross-correlation method was found to be unaffected by the Brownian motion, its reciprocal values being proportional to the flowing velocity of the scattering medium. A new technique for velocity measurement was proposed which is applicable to dense colloidal media. Less