The data storage needs of today are a fraction of what will be required ten years from now, and are monstrous compared to what was needed ten years ago. The limitations of current two-dimensional data storage formats are closer to being met, and something new, something innovative and on the cutting edge is needed to fulfill the data storage requirements of the future. I, and many others, feel that the answer is moving away from two-dimensional storage and concentrating on three-dimensional storage.
The current storage mediums that holographic data storage is met to replace are CD’s and DVD’s. The CD and DVD are nearing their upper limits for possible storage capacity and soon the general public will be demanding more storage capacity on these mediums and it will be impossible to keep offering more capacity on the same mediums.
In comparison to holographic data storage systems, compact discs and DVD’s use a single track of data, circling from the inside of the disc to the outside. Storage capacity is ample for the needs of today with anywhere from 783 megabytes for a CD (Brain, 2002) to 17 gigabytes for a double-sided, double layer DVD. (Nice, 2002)
CDs and DVDs are made in pretty much the same way… data is encoded in the form of small pits and bumps in the track of the disc. Basically a CD and DVD are just a thin piece of plastic, about 1.2 millimeters thick with injection moldings of polycarbonate plastic creating the single layer contained on a CD and multiple layers contained on a DVD. Once that has been done, the processes used to manufacture the two mediums start to differ. (Nice, 2002)
After that a CD has its layer of plastic impressed with microscopic bumps arranged as a single long spiral track of data. Once this layer is formed a thin reflective aluminum layer is put on the disc covering the bumps and a thin acrylic layer is sprayed over the aluminum. Finally the label is applied. (Brain, 2002)
For nearly twenty years devices that use lights have been the mainstay of data storage. In the early 1980s compact discs revolutionized data storage allowing the storage of up to 783 megabytes of data on a disc with a thickness of just 1.2mm and diameter of only 12cm. Then the DVD was released in 1997, which enabled 15.9 gigabytes of storage on the same size disc. Now researchers are working on a new method of storing digital data, one that will use not just the surface area of the recording medium, but go under the surface and use the volume of the medium. This new medium, called holographic memory will be able to store up to one terabyte of data in a crystal the size of a sugar cube. (Bonsor, 2002) Another positive note to add to holographic data storage is that it will allow a million bits of data to be written and read out in a single flash of light which will enable data transfer rates as high as a billion bits per second, which is fast enough to transfer an entire DVD full of data in about 30 seconds. (High density holographic data storage, 2000) Under experiemental conditions at IBM and at Stanford transfer rates of up to 100GB per second have been achieved using recent advances in components. (3D volume holographic data storage…, 2002)
Holographic data storage will require seven basic components to work:
All of the above components will work together to create your fast, high density storage system. First, the blue-green argon laser will be fired and beam splitter will create two beams of light. One beam, known as the signal beam, will go straight, bounce off one mirror and travel through the spatial light modulator, which is an LCD that shows pages of raw binary data as clear and dark boxes. Information from this page of binary code is carried by the signal beam to the light-sensitive lithium-niobate crystal (note that some systems will use a photopolymer rather than a crystal). The second beam, known as the reference beam, takes a separate path to the crystal. Upon meeting in the crystal the two beams will create an interference pattern which stores the data carried by the signal beam in a specific area of the crystal. The data is then stored as a hologram. (Bonsor, 2002)
To retrieve data, the reference beam is shined into the crystal at the exact same angle at which it entered to store that page of data. Each page of data is stored in a different area of the crystal, which is based on the angle that the reference beam strikes it. During retrieval the beam will be diffracted by the crystal to allow re-creation of the original page that was stored. This reconstructed page of data is then projected onto the charge-coupled device camera which will interpret and forward the information to a computer. The key to this is that the angle at which the reference beam is fired at the crystal must be an exact match to the original reference beam angle. A deviation of just a thousandth of a millimeter will result in failure to retrieve the needed data. (Bonsor, 2002)
Tapestry is the name of a storage system being released soon by InPhase Technologies which is an offshoot of Lucent Technologies. The write-once discs will be able to record 100 gigabytes of video or 7.4 hours of high-density material or 44 hours of standard density material. The discs are predicted to initially sell for $50 each and no price has been set for the drive as of yet. The discs resemble a 5 Ľ inch magneto-optical disk and is about the size of a CD. (Kerschbaumer, 2002)
Due to its large video storage capabilities it is felt that the first big customers for Tapestry will be broadcast entities. A system like Tapestry will allow the archiving of news and other historical material for longer periods of time and in a more modern format. Another positive note is that Tapestry is random access so if a person needs to see just a minute or two of video in the archive it will be more easily found than with tape which needs to be wound back and forth until the correct spot is found. (Kerschbaumer, 2002)
The biggest challenge InPhase Technologies faces in getting Tapestry to market is that it does not have enough money to survive until 2004, the year it expects to begin turning a profit. InPhase is actively pursuing another round of finance but since the dot com bubble burst it is a huge challenge finding anyone to invest in a new cutting-edge technology. However, there is hope in that there is a lot of goodwill toward InPhase and its competitors and there is no doubt that those who have seen the technology at work were greatly impressed. (The InPhase Plan, 2002)
Other challenges exist for Tapestry and InPhase Technologies, as well as other companies looking to market and distribute holographic data storage systems. Perhaps the biggest challenge of developing an HDSS has been the lack of availability of a suitable storage material. Most research has been done using lithium niobate, which is insensitive, costly, and has a limited dynamic range. However, a recently developed photopolymer material has been developed at Bell Labs, which shows promise. It has excellent index contrast, optical quality, and sensitivity. These materials form index changes by light-induced, irreversible polymerization that results in compositional and density fluctuations. High-density write-once read many times products can be based on this class of photopolymer. (Curtis, Wilson, et. al, 2002)
Another challenge that presents itself with this new technology is the photosensitivity of the media. Virgin discs will have to be encased in a plastic sleeve which will protect it from light. However, once they have been written on, the discs may be removed and handled. This presents a challenge in that distribution of the media will be a bit more tricky. (The InPhase Plan, 2002)
A third challenge is that the technology does not involve a master disc like is used to make millions of copies of CDs and DVDs, so the technology can not be used for mass distribution of content intended for consumers. However, there is a plan for overcoming this problem as well as the write-once issue, but InPhase, the company with the plans will not talk about it publicly. (The InPhase Plan, 2002)
It has been suggested that IBM will have a small holographic
data storage system (HDSS) ready by 2003, with early devices able to hold
125GB of data and transfer data at a rate of about 40MB per second. (Bonsor,
2002) However, HDSS devices will probably hit the mainstream in the next
three or four years. (Benoff, 2002) InPhase Technology’s Tapestry is planned
to initialize shipment by the end of 2003, with volume shipments beginning
in 2004. (Wilson, 2002)
The cost benefits of holographic data storage systems are quite obvious. A larger storage capacity compared to what is available today with higher data transfer rates will obviously benefit those who invest in the system. The medium may seem quite expensive at this point in time, but that is due to the early stages of development the system is in. Just like past innovations in computer technology, once the system hits the mainstream and mass production takes over, costs will most likely be greatly reduced and will most likely eventually be nearly comparable to the costs of owning a CD-R drive today.
Also, space will be saved for firms that archive large amounts of video. Huge amounts of reeled tape will be able to be disposed of and much smaller holographic data storage discs will replace the space-consuming reels of tape.
The HDSS is an emerging technology to keep a close eye on. With its high storage capacity possibilities along with extremely high data transfer rates the future looks bright, especially for those that require such large amounts of data to be stored. A few logistical and technical issues need to be worked out before mass production and distribution can begin. As soon as those kinks are straightened out, holographic data storage systems will takeoff, and once the cost of the technology is reduced to more attainable levels I can see the advantage of owning a holographic data storage system.
3D volume holographic data storage technology concepts, Retrieved October 12, 2002 from Colossal Storage Corporation website: http://www.colossalstorage.net/colossal5.htm.
Benoff, D. (2002). Emerging technologies: Holographic data storage. Business & Commercial Aviation, 90, 101, Retrieved October 12, 2002 from ProQuest Database.
Bonsor, K. How Holographic Memory Will Work, Retrieved October 12, 2002 from How Stuff Works, How Holographic Memory Will Work website: http://www.howstuffworks.com/holographic-memory.htm/printable/
Brain, M. How CDs work, Understanding the CD, Retrieved December 3, 2002 from How Stuff Works, How CDs work website: http://www.howstuffworks.com/cd1.htm.
Curtis, K.; Wilson, W.L.; Dhar, L.; Hale, A.; & Hill, A. Holographic data storage, finally…, Retrieved October 12, 2002 from InPhase Technologies, Technology website: http://www.inphase-technologies.com/technology/ whitepapers/pdfs/Finally.pdf
High
density holographic data storage, Retrieved October 12, 2002 from Bell
Labs, Lucent Technologies website: http://www.bell-labs.com/org/physcialsciences/projects/hdhds/1.html
The InPhase Plan. Retrieved October 12, 2002 from c|net, tech trends website: http://www.cnet.com/techtrends/0-6014-8-20013825-4.html?tag=arrow
Kerschbaumer, K. (2002). Storage no longer skin deep. Broadcasting & Cable, 132, 50, Retrieved October 12, 2002 from ProQuest Database.
Nice, K. How DVDs and DVD players work, Retrieved December 3, 2002 from How Stuff Works, How DVDs and DVD Players Work website: http://www.howstuffworks.com/dvd2.htm.
Orlov, S. (2000). Volume holographic data storage. Association for Computing Machinery, Communications of the ACM, 43, 47-54, Retrieved October 12, 2002 from ProQuest Database.
Wilson, W. (2002). The holographic holy grail. Computer Technology Review, 22, 26-27, Retrieved October 12, 2002 from ProQuest Database.