Optical memory: introduction by the feature editors.

The information age has brought with it an everincreasing demand for storage systems that have high capacity, fast data-transfer rate, and short access time. Vast memory systems are required for supporting the many storage-intensive computer applications such as multimedia, video on demand, and network-based computing. Optical memories already play an important role in existing commercial systems. The current role of optical disk memory 1magneto-optical and CD-ROM2 is driven primarily by its convenient removability and ease of replication. Progress on such planar storage systems continues. The recent demonstration of multilayer optical-disk-based storage has renewed research interest in this format, which now promises to offer significant capacity increases with minimal modification to the supporting interface 1i.e., optical and electronic2 systems. The natural extension of discrete multilayer bitwise storage has also seen significant progress with demonstrations of bit-wise volume storage using photopolymers, two-photon materials, and photorefractives. An alternative to volume bit-wise storage is volume holographic storage. Recent advances in materials, spatial-light-modulator technologies, and CCD technologies have made possible demonstrations of volume holographic optical memories that offer the desired combination of high capacity, fast transfer rate 1by means of parallel access2, and short