Photorefractive crystals for holographic storage: what are the performance limits?

Practical volume holographic storage devices are becoming more and more feasible because of the availability of cheap and efficient lasers, spatial light modulators, and electronic cameras. The critical issue is still the recording material. Phase holograms are necessary to minimize losses due to absorption and to get good diffraction efficiencies. The desired properties of the phase recording medium are a large dynamic range and a high speed. Photorefractive crystals suffer a lower dynamic range and a much lower speed. However, the performance of crystals used in demonstrator systems is far below from their physical limits. Iron-doped LiNbO₃ appears to be the best photorefractive material for storage applications so far. For several reasons: good availability, reproducible properties, excellent optical homogeneity, and detailed knowledge of the charge transport processes. Thus the analysis has concentrated on this material