Accession Number : ADA306751

Title :   Random-Access, Page-Oriented, Stimulated Echo Optical Cache Memory.

Descriptive Note : Final rept.,

Corporate Author : SRI INTERNATIONAL MENLO PARK CA

Personal Author(s) : Kachru, Ravindeeer ; Bai, Yu S.

PDF Url : ADA306751

Report Date : OCT 1995

Pagination or Media Count : 37

Abstract : This report describes a program of research to develop an innovative high-speed random-access optical cache memory. This innovation is based on a novel approach using time-domain-stimulated echo storage in smaller independent-frequency bins comprising the larger absorption bandwidth of rare-earth-doped crystals. The advantages of the approach are that memory can be stored in space, time, and frequency domain, allowing the tailoring of a flexible memory architecture to match those of the computational processor. We have instigated frequency, time, and space domain storage using a single frequency dye laser as an excitation source of optical pulses. Using Eu3+ doped Y2SiO5 crystal, we have stored and retrieved a 1.6 Kbit data stream, 40-microns long at a data rate of 40 Mbits/s in a single-frequency channel at one spatial location. By multiplying the total frequency channels available (at a single spatial spot of approx. 32), we infer a storage capacity of greater than approx. 5 x 10(4) bits per spatial spot, which is close to the theoretical storage density of 5 x 10(6) bits per spatial spot. We have achieved these results by solving the coherent saturation problem, caused by the limited frequency content of the data train, by using the pseudo-random biphase modulation technique. Our results have demonstrated for the first time that the stimulated echo memory and, in particular, the time-frequency hybrid memory, is the memory of choice for the next generation of optical random access memory.

Descriptors :   *RANDOM ACCESS COMPUTER STORAGE, *OPTICAL STORAGE, *OPTICAL PROCESSING, DATA BASES, ALGORITHMS, FOURIER TRANSFORMATION, SPATIAL DISTRIBUTION, OPTIMIZATION, DATA MANAGEMENT, ELECTROOPTICS, EXCITATION, SIGNAL TO NOISE RATIO, COMPUTER ARCHITECTURE, INPUT OUTPUT PROCESSING, PARALLEL PROCESSING, LASER BEAMS, READ WRITE MEMORIES, ECHOES, HIGH DENSITY, INFORMATION RETRIEVAL, SYSTEMS ANALYSIS, DYE LASERS, TIME DOMAIN, FREQUENCY DOMAIN, ACOUSTOOPTICS, LIGHT MODULATORS, PHASE MODULATION, PSEUDO RANDOM SYSTEMS, PHASE SHIFT, HYBRID COMPUTERS, SPREAD SPECTRUM.

Subject Categories : Electrooptical and Optoelectronic Devices
      Computer Hardware

Distribution Statement : APPROVED FOR PUBLIC RELEASE