Katsuhiro ISHII,¹ Toshiaki IWAI^1,* and Toshimitsu ASAKURA²

¹Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido, 060 Japan, ²Department of Electronics and Information Engineering, Faculty of Engineering, Hokkai-Gakuen University, Sapporo, Hokkaido, 064 Japan

(Received July 11, 1997; Accepted October 22, 1997)

The polarized intensity enhancement of the light backscattered multiply from a fractal aggregate of particles is numerically investigated using Monte Carlo simulations. It is confirmed only for the co-polarized intensity component that an effective mean free pathlength &#iota;_D defined for a fractal medium has the same physical meaning as a mean free pathlength &#iota; for a homogeneously random medium. Furthermore, co- and cross-polarized components of the backscattering intensity enhancement decrease in accordance with θ^2.16-1.03D and θ^4-1.8D in the far-field plane and with ξ^0.93D-3.94 and ξ^1.07D-3.98 in the boundary plane between the scattering medium and the air. Therefore, the two-dimensional Fourier transform relation is satisfied only between the co-polarized intensity distributions in the far-field and the boundary planes but not the cross-polarized ones with the accuracy of the numerical simulation. Finally, we notice the applicability of the enhanced backscattering light to estimating the dimension of the absorbent fractal medium on the basis of the result that the slope of the intensity decay of the intensity peak is directly proportional to the dimension of the medium but is independent of the absorption.

Key words : fractal aggregates, enhanced backscattering, absorption, free pathlength distribution, Monte Carlo simulation

*iwai@hikari.hokudai.ac.jp