Progress in read–write fast–access volume holographic data storage

We review recent progress made towards commercializable read–write, fast–access holographic data storage. This includes a recent demonstration of high areal density holographic storage [1], systems architectures for extending this high density to high capacity using phase–conjugate readout [2], and recent experimental progress along these lines. Other topics include using signal processing to relieve alignment and distortion constraints [3], optical elements for improving beam uniformity [4], and most importantly, requirements and prospects for improved photorefractive materials for two–color, gated nonvolatile holographic storage [5].