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Microholographic Data Disk for Archival Storage

Project description


Optical, opto-electronic, photonic functional components
Digital disc storage enters the third dimension

European researchers have created a prototype holographic technology that could ultimately store one terabyte, or 1,000 GB, of data on a disc the size of a DVD.

With the Microholas holographic data-disc storage system, a good chunk of the internet could be stored on a few hundred discs. The advance would provide a very simple and comparatively cheap archiving system for digital libraries, server farms and public and private databases. The system works by layering data and varying the laser wavelength or recording conditions to create a three-dimensional 'stack' of data in a tiny space.

50 data layers

Currently, standard data-disc technology uses surface structures only, but the system created by the EU's Microholas project works by using nanostructures throughout the depth of the disc. The system creates a disc that stores data in three dimensions. The project's researchers entered the third dimension by applying two lasers to the disc. Refractive and interference patterns created by the two lasers create a three-dimensional holographic grid matrix.

This grid matrix is composed of a series of layers, and the prototype has 50 data layers in its grid.

Then the researchers used wavelength multiplexing - simply lasers of different frequency - to access the different layers. Using this technique, the team successfully created a DVD-sized disc demonstrating a capacity of 150GB. The ensemble is called a microholographic disc (MHD).

Terabyte in 2010

The team developed a complete system composed of recorder, reader and disc, and they now hope to perfect the technology to create a terabyte model by 2010. By comparison, a double-layer bluray disc, the largest DVD-sized storage medium currently available, can hold just 50GB of data.

The promise of a new data technology capable of storing 1 terabyte of data on a DVD disc represents a staggering advance in the field. To put the advance in perspective you need to compare the storage capacity with something really, really big, like the internet, for example.

In 2003, the surface internet - fixed web pages - was 167 terabytes, according to the Information Management & Systems department at the University of California, Berkeley. So just 200 MHD discs could store the entire surface web. The technology is not intended for media distribution, like movies and software. The researchers will focus on developing it for digital archiving and long-term storage.

As such, the Microholas project is very much of the moment. Increasingly, the world's cultural heritage is stored digitally, but current digital media technology is not as durable as its analogue counterparts, such as books.

Books can last hundreds of years, but digital optical storage like DVDs have an upper theoretical limit of 50 years, according to a British Library report.

It may seem counter-intuitive. Plastic lasts a long time. But digital information on a DVD is very delicate. If there is any degradation in disc integrity, the data becomes unreadable, and 50 years is the upper limit.

A robust data-preservation strategy must replace aging digital disks regularly, and that gets expensive unless you have a low-cost, high-density storage system. It is a serious problem.

Digital Dark Age

Researchers at the Microholas project warn that society could face a digital 'Dark Age', with vast tracts of cultural heritage lost, if a robust preservation and storage strategy is not developed.

Much of the world's analogue culture patrimony, such as books, exists in both digital and analogue media. But much, much more only exists digitally.

MHD offers the low-cost, high-density storage answer to the digital preservation question. The project team believes the microholographic discs could be manufactured cheaply and hopes to attract the interest of manufacturers.

The overall objective of MICROHOLAS is to implement the microholographic technique for optical storage on CD/DVD-like disks for digital data. The project aims at long term storage by utilizing periodic nanostructures in the disk volume rather than on the surface as in conventional optical storage systems. A prototype read/write device will be designed and constructed to demonstrate the feasibility of volume microholographic storage on a rotating removable disk. Bit-formatted data is stored as microholograms in a thin photopolymer layer. The microholographic recording technique allows for an increase of the storage capacity far beyond the limits of current DVDs and next generation blue-Ray disks by applying wavelength multiplexing combined with multilayer storage. The proposed new and original system relies on and benefits from well established CD and DVD technology. This will ease realizing the device and open a viable route for Terabyte storage. The design and construction of the demonstrator test bed will be accompanied by research focused on characterization and development of photopolymers with improved properties as required for long-term and Terabyte storage. A thorough testing programme starting from initial laboratory measurements up to dynamic tests with the device under development will be undertaken to optimize the design at all stages of the technological realization. In the final phase an experimental system will be tested for data archiving. The implementation of microholography for digital data storage on a disk has the potential to become a major breakthrough in realizing Terabyte optical storage. Additionally, innovation beyond the state of the art is expected with new and improved photopolymers as well as with optical and laser components required for the device. At the end of the project a microholographic storage disk and a demonstrator device will be available which will have been successfully tested for archival storage.

Keywords

Call for proposal

FP6-2003-IST-2
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Coordinator

TECHNISCHE UNIVERSITAT BERLIN
Address
Strasse des 17 juni 135
10623 Berlin
Germany

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Region
Berlin Berlin Berlin
Activity type
Higher or Secondary Education Establishments
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EU contribution
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Participants (5)