Accession Number : ADP006727

Title :   Holographic Storage Capacity Estimate for Photorefractive Media,

Corporate Author : COLORADO UNIV AT BOULDER DEPT OF ELECTRICAL AND COMPUTER ENGINEERING

Personal Author(s) : Fredericks, George ; Lahrichi, Adil ; Johnson, Kristina

Report Date : 22 MAY 1992

Pagination or Media Count : 5

Abstract : A fundamental argument based on the number of multiple exposure volume holograms that can be distinguishably recorded and retrieved in a photorefractive database places an upper limit on of about a terabit per cubic centimeter on the storage density'. However, the practical limit is much smaller and depends on the bit error rate (BER) and read out band that are desired. The BER that will be experienced on reading one set of equal diffraction efficiency multiple exposure volume holograms will depend on the signal to noise ratio at the output detector. The signal will depend on the laser power in the read beam and the diffraction efficiency of the hologram. The noise will consist of intrinsic detector noise and crosstalk noise. The crosstalk noise analysis depends on the method used to address multiple holograms or pages of information. One method is Bragg selection or angular addressing dressing. In this case each hologram is recorded with different angles between object and reference beams. This produces holograms with different grating vectors. Read out of a particular page then occurs when the reference beam satisfies the Bragg condition with the grating vector of the hologram containing that page. Crosstalk can occur when light is scattered from the read out beam from crystalline imperfections. When a large number of pages with closely spaced Bragg angles have been recorded, the scattered light will have a very high probability of addressing another page giving rise to crosstalk noise.

Descriptors :   *OPTICAL STORAGE, *HOLOGRAPHY, ANGLES, CROSSTALK, DETECTORS, DIFFRACTION, EFFICIENCY, ERRORS, HOLOGRAMS, LASERS, LIGHT, NOISE, OUTPUT, POWER, PROBABILITY, RATIOS, SELECTION, SIGNAL TO NOISE RATIO, SIGNALS, STORAGE, DATA STORAGE SYSTEMS, REFRACTION, SYMPOSIA.

Subject Categories : Holography
      Computer Hardware

Distribution Statement : APPROVED FOR PUBLIC RELEASE