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Holographic Storage Memory for Computer Systems

written by: Lamar Stonecypher•edited by: M.S. Smith•updated: 1/28/2012

Long a staple of science fiction, holographic data storage on physical media is now available for computer systems. The industry is young and the entrance pricey, but it offers many benefits over conventional storage. The creation of this device required science, dedication, and good luck.

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    Long the stuff of science fiction, holographic memory is often portrayed as being made of glass or crystal. Examples are the rectangular glass memory of the HAL 9000 computer in the movie “2010 – The Year We Make Contact" and the numerous control crystals in the television show “Stargate Atlantis."

    2008 is the year that holographic memory, if one company has anything to do with it, goes mainstream.

    The company is inPhase Technologies of Longmont, Colorado, and the product is the Tapestry 300R holographic reader/writer.

    Here’s what it looks like. (Click the image to enlarge.)

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    Tapestry Angled 

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    Holograms are not a recent development. They’ve been around since the 1940s and are found on credit cards and on Genuine Windows® Certificates of Authenticity on PCs.

    The basic idea is that if you split a laser beam with a prism or mirror and then modulate or vary the intensity of the second stream and then combine it back with the primary stream, an interference pattern is created. That’s the basis of laser light shows and holographic images that seem to float before our eyes.

    If you keep the second stream intact, it becomes a reference beam. If you then modulate the primary beam by passing it through a special filter called a spatial light modulator or SLM, it creates an interference pattern in the beam. At the point where the reference beam and the interference pattern are focused and intersect, a hologram is created in a light sensitive storage medium.

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    media 

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    A chemical reaction occurs in the storage medium that “sets" the hologram. It’s built from all the digital 1’s and 0’s in the data being recorded, but instead of like grooves in a vinyl record or the microscopic valleys and hills of a CD-ROM, the hologram is written all at once, in one flash of the laser. The recording, if somehow viewed from the side, would be similar to a checkerboard with a million squares.

    To read data from the disc, the reference beam, at the same precise angle it was in when the data was written, is focused through the hologram set in the disc. A detector array reads the image, and the data is converted back into 1’s and 0’s.

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    The story of how inPhase came to bring this product to market is based on science, research, and serendipity.

    Originally a spinoff of Lucent Technologies, which was spun off from Bell Labs, inPhase Technologies started up in December, 2000. They provided the technology and invented processes and hardware (like the recording media). The broader market provided the hardware that enabled their theories and led to the product offering.

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    For examples of serendipity, detector arrays were until recently costly, poor performers. CMOS sensors used in digital cameras were found to be both readily available and cost-effective. Lasers were not only costly, but also unreliable in 2000. Now red and blue lasers are used in many consumer devices and reliability has greatly improved. Spatial light modulators were slow and had poor contrast. Ferroelectric modulators and digital mirrors used in digital projectors and TVs answered that problem.

    Good engineering and invention did the rest for inPhase. They invented Tapestry™, the recording medium, and the process, called ZeroWave™, used to manufacture the discs.

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    The medium currently can hold 300 GB in a single disc and the Tapestry 300R reader/writer can produce a 20 MB/sec transfer rate. That’s not earth-shattering, but the first applications of this technology will be concerned more about long-term storage than media read/write speed. The competition is data recording tape, which has around 120 MB/sec reads, but needs to be re-recorded about every five years, and hard disc drives come nowhere near the expected fifty-year archive life of a Tapestry disc.

    Tapestry discs are “write once-read many" media. Since there’s no physical contact between the media and the machinery, the discs should be good for literally millions of reads. The discs are stable and designed to work, and be stored in office environments, not dark, air-conditioned closets or glass-enclosed computer centers.

    Networking-wise, the 300R offers SCSI, Fiber Channel, and Ethernet connections.

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    After years of waiting, we are finally at the dawn of the era of holographic storage. This is a very young and early product. inPhase hopes to ramp up to +1 terabyte capacity and +120 MB/sec reads within a few years.

    How much does it cost? You need to frame that question somewhat by asking what it costs compared to data recording tape machines and multiple, redundant hard drive arrays – setups often found in data centers for large businesses.

    We’re not likely to see one on our desktops in the next few years. The 300R is $15,000 and the discs are $180.

    Then again, a year ago, one could not purchase holographic storage for a computer system at ANY price. Now it’s possible.

    And inPhase pulled it off. Congratulations (and business success) are due to them for this achievement.

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