Accession Number : ADA329446

Title :   Holographic Random Access Memory.

Descriptive Note : FInal rept. Jun 94-Jun 96,

Corporate Author : CALIFORNIA INST OF TECH PASADENA

Personal Author(s) : Psaltis, Demetri

PDF Url : ADA329446

Report Date : MAY 1997

Pagination or Media Count : 77

Abstract : 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 10%(A). 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.

Descriptors :   *RANDOM ACCESS COMPUTER STORAGE, *OPTICAL STORAGE, *HOLOGRAMS, FRACTALS, IMAGE PROCESSING, DATA STORAGE SYSTEMS, TIME DIVISION MULTIPLEXING, TWO DIMENSIONAL FLOW, ACOUSTOOPTICS, ACOUSTIC HOLOGRAPHY.

Subject Categories : Computer Hardware
      Holography

Distribution Statement : APPROVED FOR PUBLIC RELEASE