29 Mar 2007
Storing one terabyte of data on a DVD-sized disk has just moved a step closer. Mempile has demonstrated that its TeraDisc technology can store nearly 300GB on a single disk, with larger capacities on the way.
Existing optical disks can only store data on a limited number of defined layers because they rely on light reflection through semi-transparent media. In contrast, TeraDisc exploits nonlinear two-photon technology to enable 3D recording of data in transparent virtual layers throughout the disk's volume.
The technique uses a red laser, able to focus at any point in a disk's volume. The laser acts on light-sensitive chromophores in the disk, switching them between two distinct states to "write" data. Reading the data back relies on the differing fluorescence of "written" and "unwritten" molecules under laser excitation.
Only those molecules at the focus of the laser are affected, allowing data to be written selectively to very small volumes of the disk. Other chromophores at different depths through the disk are unaffected, so once written the layers of data are effectively transparent until brought into focus.
Mempile's demonstration has shown that a disk with 0.6 mm thickness of active material could contain 100 layers, enabling almost 300 GB to be recorded onto the disk and successfully read back. Doubling the active thickness to that of a standard 1.2 mm optical disk should raise capacity to at least 500 GB.
Beth Erez, Mempile's executive vice president, told optics.org that plans are in place to refine the optical system and the composition of the active material to squeeze in even more data. Novel tracking algorithms will also need to be developed to allow reliable accessing of data at varying depths within the disk. The ultimate aim is to record 200 layers of 5 GB each onto a standard size disk - the magic 1 TB.
One issue on the horizon will be the need for new equipment to record and play back the discs. TeraDisc products will introduce another new disk format for data storage, although some degree of backwards compatibility with existing formats should be possible. But Mempile are confident that TeraDisc will have broad appeal.
"TeraDisc technology will lend itself to high volume manufacture," said Erez. "We see it as filling a fast-growing void in the consumer market for permanent records and backups of digital content." Business sectors like health and finance are finding that their archival needs can double every year, and any organization engaged in video monitoring needs substantial data storage. Having 1 TB on a disk would be very attractive to them too.
Mempile are working closely with disk manufacturer Memory Tech and chemicals company Arkema to develop the technology further, and estimate that the final products could be commercially available in about 2010.
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