The Influence of Random Media on the Propagation and Depolarization of Electromagnetic Waves

Citation

Harris, Jerry Michael (1980) The Influence of Random Media on the Propagation and Depolarization of Electromagnetic Waves. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/XH76-NK15. https://resolver.caltech.edu/CaltechETD:etd-10162006-082641

Abstract

Electromagnetic wave propagation and depolarization in an inhomogeneous medium having random fluctuations in its permittivity are studied. The continuous space-time permittivity fluctuations are taken to be frozen-in, homogeneous, and isotropic. We find that the essential effect of the random permittivity is to destroy the time coherence and spatial orthogonality of the vector components of an electromagnetic wave penetrating the medium.

To study this problem, we develop a unique discrete model for the continuous random medium by dividing the volume occupied by the random inhomogeneities into independent elementary scattering volumes. Scattering by each of these elementary volumes is analyzed to obtain the complex amplitude and polarization of the single scattered field. Then multiple scattering among the many elementary volumes is used to estimate the composite values for scattering per unit length and depolarization per unit length of the medium. The manifestation of scattering in the medium is the generation of an incoherent or fluctuating electric wavefield and a coherent or average electric wavefield. It is shown that the total electric wavefield propagating in the medium satisfies an integral equation which is directly reducible to the classical equation for radiation transfer.

A novel result of this study is that only two phenomenological parameters are needed to describe the penetration of the wave into a plane-parallel medium, when a polarized plane wave is normally incident. These two parameters appear as diffusion constants in expressions for the solution for the coherency and Stokes matrices. These solutions simply describe how wave energy is progressively converted from the initially coherent and polarized field to an incoherent and unpolarized field as the wave propagates. An initially polarized wave is gradually depolarized, yielding a completely unpolarized wave deep into the medium.

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