Coherent backscattering of light from a polydisperse random medium as a model of fractal aggregations of particles

The reproducible models of biomedical optics, the measurements of chemical compounds, the aggregations of particles and so on require the statistical space-time properties of the multiply scattered light in laboratories to be analyzed quantitatively. A cluster-cluster structure in fractal media is replaced with a polydisperse random medium by renormalizing a cluster to a particle. As the particle size-distributions, a simple summation of particles with two radii, a Gaussian function and a power law function were used in numerical simulations. The light scattered from particles inside a cluster affects a decreasing rate of the backscattering intensity cone but not a relaxation time of autocorrelation functions of the time- varying intensity. On the contrary, the movement of the cluster affects strongly the relaxation time through the diffusion constant but not a decreasing rate of the backscattering intensity enhancement. As a result, it is concluded that the temporal autocorrelation functions of the time-varying light intensity scattered multiply from the cluster-cluster structure are applicable to measure the averaged cluster size of aggregations.