FARADAY-EFFECT AND MULTIPLE-SCATTERING OF LIGHT

The presence of a magnetic field in an optically active medium produce s a rotation of the polarization of light: it is the well-known Farada y effect, which breaks the time-reversal symmetry. The averaged light intensity in the multiple scattering of light by disordered systems is described by the weak-localization theory based on the direct and rev erse sequences of scatterings, which are founded on the time-reversal symmetry. The multiple scattering of electromagnetic (vectorial) waves by spherical particles is considered in the presence of a magnetic fi eld. We have shown that the electric field of the reversed path can be obtained from the direct one by a simple matrix transposition. In sys tems of reduced dimensionality (1 and 2), we have shown that for the s ame polarization channel, the peak of the backscattering cone is not a ffected by the Faraday effect even though the time-reversal symmetry i s broken. The intensity correlation function is obtained for a one-dim ensional system. This simple model furnishes two results: (i) even tho ugh the wave vector is randomized, there is no decorrelation of the po larization for paths of the same length and (ii) the correlation funct ion has an oscillatory behavior as a function of the magnetic field. I n three dimensions, we have calculated analytically the attenuation of the backscattering cone as well as the decorrelation length for the m ultiple Rayleigh scattering. Mie scattering has been considered by Mon te Carlo simulations. In the diffusion regime (thick slabs) our result s are in accord with previous results and with experiments. Neverthele ss, for the intermediate regime in transmission, we have found oscilla tions of the intensity correlation as a function of the magnetic field . For reflection and strong magnetic field, we have observed the conve rgence of the enhancement factor to nontrivial asymptotic values.