- Squeezing a terabyte of data, the equivalent
of 1,600 compact discs, on to a single CD-sized hologram may soon be possible.
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- It is also believed it will be possible
to read the data at one gigabit per second - 100 times faster than a DVD
drive.
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- The advance, reported in New Scientist,
has been made possible by a new kind of polymer, developed at the Bayer
Institute in Leverkusen, Germany. The scientists expect to make the technology
work within five years.
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- Holography is attractive because, in
the next few years, traditional two-dimensional storage in hard drives
and DVDs is likely to reach its data density limit. However, the problem
has been to find a way to read the information stored in the hologram without
erasing it.
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- Bayer's new photo-addressable polymer
(PAP) has chain-like molecules which become aligned when polarised laser
light passes through and stay like that even after the beam has been turned
off. The alignment can then be read by an unpolarised laser beam without
affecting the data.
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- Easier mass production
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- Hans Coufal, a holographer at IBM's Almaden
Research Center in San Jose, California, believes another advantage of
using polymers is that they can be shaped more readily than crystals, making
them easier to mass-produce.
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- "But up to now, polymer materials
are not available in the thickness needed to store sufficient amounts of
data," says Coufal.
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- Bayer's Thomas Bieringer agrees this
aspect needs addressing: "We do have one polymer which stores holograms
in one millisecond, but the polymer has the problem of being too thin and
in holographic data storage you need thick samples to maximise the number
of images stored."
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- The Bayer team has narrowed its choice
of PAP down to just five out of 300 that it has tested. The ideal, he says,
is to combine all the desirable features of these five substances into
a single polymer.
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- Bieringer's aim is to store a thousand
data images, each 1024 by 1024 pixels, on a single cubic millimetre of
the polymer, and to be able to read each image in a millisecond.
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