Acousto-optical imaging of thick biological tissues using a photorefractive detection

The coupling of light and ultrasound within biological tissues allows to measure localised optical contrasts in the tumors detection. Light at the output of the sample contains a contribution from the standard scattered photons, and another one from light that has crossed the ultrasonic volume, that is frequency shifted by the ultrasound wave. These so-called tagged-photons are carrying the acousto-optical contrast information, as the number of tagged photon is dependent on the number of photon transmitted by the interaction area, and thus to the local absorption of the media. A drawback of this technique comes from the speckle structure of the transmitted waves caused by the multiple-scattering process occurring in the biological tissue, so that the extraction of the useful information generally requires an interferometric detection with a high optical etendue