Holographic Random Access Memory.

We designed and demonstrated a fully working, large-scale random-access holographic memory. The recording medium is a Fe-doped LiNb03 photorefractive crystal. The storage capacity of the memory is limited by the dynamic range and geometric limitation. The number of holograms stored at a certain location in the crystal is mainly limited by the dynamic range. To further increase the storage capacity, holograms can be stored at different spatial locations in the crystal. The total number of storage locations is restricted by the geometric limitations of the optical system. Three multiplexing techniques -- angle, fractal and spatial multiplexing are employed to superimpose multiple holograms in the recording medium with the help of a custom-designed segmented mirror array. The memory consists of 16 vertically spaced locations on the recording medium, a LiNb03 crystal, each containing 10,000 holograms. The data storage on each of the 16 locations is organized as 4 fractal multiplexed rows of 2,500 angularly-multiplexed holograms. We successfully demonstrated the storage of 160,000 holograms in the system by recording 10,000 holograms on each of the top, center, and bottom storage locations and 1,000 holograms on each of the 16 locations. We achieved an average bit-error probability on the order of 10A. By using an acousto-optic deflector AOD as the angle scanner, we achieved a random access time in the order of 100 microseconds to the 1,000 holograms stored by angle multiplexing. In the latest progress towards a practical non-volatile memory system, we recorded and thermally fixed 1,000 holograms with no degradation in the error perlormance.