Picosecond magneto-optical phenomena in turbid media: toward magneto-optical characterization of highly scattering biological samples.

The behavior of a Faraday-active turbid medium under ultrafast optical excitation is investigated. As the degree of polarization of early arriving photons is mostly preserved during the first 100 ps after the arrival of the ballistic component, the possibility of using the magneto-optical rotation of the light polarization as a new tool for tissue characterization is addressed. A technique is proposed for determining photon-scattering statistics in turbid biological media. The analysis is performed on the basis that photons trapped in multiple-scattering events leave the medium with larger induced rotation angles. A measurement of the magneto-optical rotatory power of turbid biological samples is possible if only the early arriving unscattered photons are probed.