Dielectric photorefractive crystals as the storage medium in holographic memory systems

The potential behavior of dielectric photorefractive (DPR) crystals as the storage medium in holographic memory systems (HMS’s) is analyzed. First the theoretical origins of the DPR effect and the experimental evidence indicating its existence are briefly reviewed, and the diffraction efficiency of DPR crystals is discussed. The potential performance of DPR crystals as the storage medium in HMS’s is then assessed in terms of the writing energy, the storage density, and the retrieval capability. A figure of merit, F, which characterizes the overall performance of photorefractive storage media, is defined. It is found that F of DPR crystals is 2 orders of magnitude larger than F for LiNbO₃;Fe. It is pointed out that this advantage stems from low erasure during readout, which characterizes DPR crystals. Finally, the limitations of DPR crystals are briefly discussed.