High-speed, high-density, coherent time-domain optical memory. Final report, 1 September 1990-31 August 1993

Ravinder Kachru, Xiao A. Shen

Published Nov 1, 1993• 0 citations

Abstract

The objective of this research was to quantitatively evaluate the concept of time-domain optical memory (TDOM) using the hole-burning mechanism. The TDOM concept offers both high speed and high memory density. The advantage of TDOM over traditional semiconductor memory is its inherent parallelism, which allows data to be stored and retrieved from the memory at much higher speed. The practical success of the proposed memory, therefore, depends critically on-among other issues-the storage, retrieval, and processing of images. In addition, new data storage techniques are needed to implement a practical memory. The last three years of this research program have focused on (1) development of new phase modulation techniques to enhance the storage, retrieval, and integrity of the stored information; (2) experimental studies of image storage and phase conjugate retrieval; (3) Image processing; and (4) practical holographic storage of images by using the hybrid time-frequency approach. Specifically, SRI demonstrated data encryption by phase modulating the read and write pulses. Image correlation and convolution was demonstrated and its implication for pattern recognition examined. Finally, this laboratory demonstrated high-fidelity random access and retrieval using holographic storage in Pr3+: YA103 with a single-frequency ring laser. These experiments have clearly demonstrated the practical viability ofmore » TDOM with existing technology. In the next stage of the research, the performance Issues such as bit-error-rates, signal-to-noise ratios, and laser stability need to be addressed. Stimulated photon echoes, Optical memory, Image processing, Pattern recognition, Phase conjugation.« less

Related papers

High-speed, high-density, coherent time domain optical memory

Ravinder Kachru, Xiao‐An Shen

Our goal is to quantitatively evaluate the concept of time-domain optical memory (TDOM) based on the stimulated photon echo technique and to prepare for the development of a working prototype. Earlier feasibility studies at SRI International showed that TDOM can store not only digital data in the form a series of on-off laser pulses but also two-dimensional (2-D) images with the same read/write speed. Despite work at SRI and elsewhere, until now the use of TDOM for 2-D images has not been carefully examined and the quality of echo images and their inherent spatial resolution have not been explored. These issues have an important bearing on TDOM as a high-speed, high-density storage device. This year, we focused on using the stimulated echo technique for 2-D image storage and image processing. Specific tasks included incorporating a gated intensified charge-coupled device (CCD) camera system for detecting echo images, digitally recording the echo images, and optimizing the optical system. We have also extended the earlier feasibility study on stimulated-echo-based, 2- D image storage and image processing and demonstrated storage and retrieval of the high-quality, high-resolution echo images. In addition, we demonstrated for the first time that nanosecond pattern recognition can be achieved using the stimulated echo approach. (Author)

sriNov 1, 19930 citations

High-speed optical recording with rare-earth-doped hole-burning materials

Ravinder Kachru, Xiao A. Shen

We are developing a high density, high speed optical memory, using rare-earth doped hole- burning materials. These materials are theoretically capable of achieving storage densities of 1000 Gigabits/cm3 at input/output (I/O) rates of several gigabits/sec. One remarkable attribute of this storage concept is that both the temporal and spatial information encoded on a laser beam can be stored. Because both the temporal and spatial information can be stored, digital data can be recorded serially as a data or packet stream as well as holographically using the page format. During the past year we have achieved a breakthrough in demonstrating random access holographic data storage at high frame rates. Five hundred holograms were stored and retrieved with very good fidelity at 30 Hz (video rate). Each holographic image with 512 multiplied by 488 pixels could be randomly accessed during the storage and retrieval process. This frame rate is the highest demonstrated frame rate for any optical technique. This breakthrough was achieved through the invention of a memory architecture that allows multiple holographic frames to be stored without any mechanical beam scanning. In this new architecture multiplexing of 500 holograms was achieved by stepping the laser frequency over a range covered by high speed acousto-optic modulators (AOM).

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEJan 15, 19960 citations

High-Speed Holographic Recording of 500 Images in Hole Burning Rare-Earth Doped Crystals

Ravinder Kachru, Xiao A. Shen

One of the unique and perhaps the most attractive features of an optical memory is its ability to store and retrieve information in a bit-parallel format.1-3 Recently, we have proposed a new scheme for parallel data storage in TDOM.4,5 This scheme was proven to be practical and can be implemented with existing technologies. In a proof-of-principle experiment, four wavelength-multiplexed single-page volume spectral holograms, generated with black-and-white transparencies, were successfully stored in a single spatial location at a speed of approximately 23 μs/frame. The experimental results project system's input/output bandwidth to exceed 40 Gbps, two orders of magnitude faster than a semiconductor cache memory.

Topical Meeting on HolographyJan 1, 19960 citations

Time-domain optical memory for image storage and high-speed image processing

Xiao A. Shen, Ravinder Kachru

We present an experimental study on the use of the time-domain optical memory for image storage and high-speed image processing. We focus on examining the fidelity of the recalled images and their spatial resolution as well as various image-processing operations offered by the memory. The recalled images were found to be of good quality because of their phase-conjugate nature. This unique feature further motivated us to examine the feasibility of fiber optics being used for image transmission, an issue important to the development of such a memory device. Two primary processing operations, two-image convolution and correlation, were demonstrated, and implications of the results for high-speed pattern recognition and optical interconnections are discussed.

Applied OpticsOct 10, 199314 citations

Time-Frequency Domain Memory and Processing

David L. Huestis, Gregory W. Faris, E. Arons

This report summarizes the results of a 3-year program of research on the physics and technology needed to develop high-performance optical memory and optical processing systems based on the concept called the stimulated photon echo (SPE). The research goals were investigation, demonstration, and improvement of signal strength and fidelity, architectures and algorithms, and materials properties for optical storage and in-memory processing. Key accomplishments were (1) development and demonstration of efficient algorithms for threshold discrimination and bit-error-rate reduction in retrieved binary images with large in-frame and frame-to-frame intensity variations; (2) demonstration and characterization of information storage in Erbium-doped crystals using 1.5-micron diode lasers compatible with fiber optic communications; (3) demonstration of improved phase-encoding schemes for in-memory temporal correlation of 1.5-micron pulse trains; (4) development of concepts for high-performance radar applications based on SPE optical memory for time-delay control of the transmitter array and in-memory image processing of the return signals; and (5) hosting the AFOSR Contractors' Meeting, "Optoelectronic Information Processing."

Feb 28, 20020 citations

Optical Memories and Processing in Time- and Frequency Domain

Baozhu Luo

Spectral hole burning and photon echoes are the techniques for frequency-selective optical memories, which have the potential to increase areal data storage density by a factor 10**7. They also have the capability to perform in-memory data processing. In this thesis, several materials and techniques for optical memories in the frequency- and time domain have been investigated. In the frequency domain, ways to increase the storage density and the working temperature were studied using photon-gated spectral hole burning materials of the metal-tetrabenzoporphyrin derivatives. A selection rule for the electron acceptors in the donor-acceptor electron transfer systems was deduced. By doping the material with two different donors a maximum inhomogeneous line width of more than 30 THz was achieved. A polarization holographic technique was established for the formation and detection of spectral holes. Our results indicate that this technique can provide a better signal-to-noise ratio than that achieved by a conventional holographic technique, in particular for samples of poor optical quality. In the time domain, magnetic field-induced and the intensity-induced dephasing processes were studied in Pr3+ doped in a YAlO3 crystal and a Y2SiO5 crystal, respectively. As a step along the route to make photon echo based optical processing possible, the amplification of photon echo signals by the use of a fiber amplifier (Pr3+-doped ZBLAN) was demonstrated. A gain of 45 was achieved. The erasure of stored data using photon echoes has also been investigated. A technique to diagnose the phase and frequency stability of a light source by the photon echo erasure process was proposed and illustrated. An approach to bit-selective data erasure, that is free from laser phase and frequency fluctuations, is also suggested. A concept for an arbitrary shape pulse generator based on photon echoes and hole-burning was experimentally and theoretically studied. Finally, a comparison between the properties and capabilities of spectral hole burning and photon echoes was made.

Lund reports on atomic physicsJan 1, 19980 citations