Theoretical description of the photorefractive detection of the ultrasound modulated photons in scattering media.

Acousto-optic imaging of thick biological tissues can be obtained in real-time with an adaptive-wavefront holographic setup, where the holographic media is a self-developping photorefractive crystal. As a consequence, the interference signal resulting from the acousto-optic effect can be easily collected with a high etendue and fast single photodetector. We present a statistical model of the field propagating through the scattering media and show why the various acoustic frequency components contained in the speckle output pattern are uncorrelated. We then give a detailed description of the signal measured through the photorefractive effect, in order to explain the quadratic pressure response observed for the two commonly used configurations setup e.g an amplitude or a phase modulation of the ultrasound.