Photorefractive holography with phase conjugate of signal beam

Photorefractive crystals are one of the most efficient nonlinear optical media for recording real-time holograms with relatively low intensity requirements. This is because of their practically unlimited recyclability and they can be recorded and erased in this medium with sufficiently high sensitivity. Innovative geometries have been proposed by various authors to record holograms in these crystals with and without using applied electric field across the crystal in both two and four wave mixing geometries respectively. But, in all these cases the diffraction efficiency was not comparable with the conventional holography using photographic emulsions and this will be evident when one records real-time holographic interferograms using photorefractive crystals. In this paper we propose a new geometry for recording high efficient holograms in the photorefractive media using the phase conjugate beam of the signal beam itself as the other writing beam. Diffraction efficiencies increase by four times and PR gain increases two times in this case.