Depth-resolved holography through turbid media using photorefraction

A technique based on photorefractive holography for imaging objects obscured by a scattering medium is presented. Using ultrashort pulse illumination, depth-resolved whole-field images of three dimensional objects embedded in scattering media have been obtained. Bulk photorefractive crystals and photorefractive multiple quantum-well (MQW) devices have been investigated as the hologram recording element. Images have been obtained through media of up to 16 scattering mean free paths with a system based on bulk rhodium-doped barium titanate (Rh:BaTiO₃). Using MQW devices, a real-time image acquisition (<0.4 ms) has been demonstrated when imaging through eight scattering mean free paths. The relative merits of photorefractive holography are discussed, including its potential to provide a higher dynamic range of detection than traditional photographic film based or electronic holography. This could be important for in vivo imaging through biological tissue