|
|
Holographic Data Storage
Holographic and photorefractive data storage systems
|
Demon II -- IBM Research's test platform for holographic data storage
Pictured is Geoffrey Burr, research staff member, IBM Research's Almaden Research Center (San Jose, Calif.) and the "DEMON II" test platform, which was built to explore high density holographic data storage under the DARPA-sponsored HDSS consortium. Burr and colleagues used Demon-II to demonstrate an areal density 80 times higher than a DVD optical disk. (The IBM result is 254 Gbits/ sq. inch, or 394 bits/sq. micron. DVD single-layer density is 3.0Gbits/sq.inch or 4.7bits/sq.micron.) This density corresponds to about 1 percent of the theoretical limit in volumetric density for holographic storage of one bit per cubic wavelength.
In the lower right corner, a 30mm-diameter beam is directed up and onto a spatial-light modulator (right) with 1 million pixels, each representing a data bit. This data-bearing object beam then enters the holographic data storage crystal (center), where it meets the narrow reference beam entering from lower left. Data is stored when the interference pattern created by the two beams changes the optical properties of the crystal within the overlap region. Multiple holograms can be stored in the same volume by varying the angles of the beams. For readout, a reference beam projected into the crystal selectively reconstructs -- according to its input angle -- only one of the 1,000 superimposed holograms, producing the appropriate data-bearing object beam, which can be detected by the CCD camera (left).
DARPA = Defense Advanced Research Projects Agency
HDSS = Holographic Data Storage Systems
Holographic Data Storage research IBM-Almaden
IBM is one of the leaders in two recently completed industry, university and government research collaborations in holographic data storage: Photorefractive Information Storage Materials (PRISM) and Holographic Data Storage Systems (HDSS).
The PRISM project was aimed at developing optically sensitive materials optimized for storing holograms and an understanding of the various tradeoffs that must be made between mutually exclusive performance parameters. The HDSS project took the next step: developing the other hardware technologies needed for practical holographic data storage systems and integrating them into demonstration systems (see latest "DEMON" image).
1) Closeup of PRISM holographic materials test stand. The crystal containing holograms is at the top center.
2) Multiple exposure shot shows the multi-angle testing capability of the PRISM test stand.
This second "multiple exposure" photo can be seen at: http://www.almaden.ibm.com/almaden/media/
fourth row, left-hand image.
Assoicate Retrieval in Holographic Data Storage
The unique ability of holographic data storage to instantly locate similar features stored within a crystal is shown. A data pattern (the letters "IBM") is projected onto the top of a crystal storing thousands of holograms. The stored holograms diffract the incoming light out the side of the crystal, with the brightest spots identifying the location of the data that most closely resembles the input pattern. Such "associative retrieval" is a unique property of holographic data storage that has long been predicted, but was first demonstrated by IBM Research scientists (at its Almaden Research Center, San Jose, Calif.) in [date]. Associative retrieval is expected to be especially useful when holographic data storage is used to store large databases that must be searched rapidly.
|
|
