A new optical recording method could pave the way for data discs with
300 times the storage capacity of standard DVDs, Nature journal
reports.
The researchers say this could see a whopping 1.6 terabytes of
information fit on a DVD-sized disc.
They describe their method as "five-dimensional" optical recording and
say it could be commercialised.
The technique employs nanometre-scale particles of gold as a recording medium.
Researchers at Swinburne University of Technology in Australia have
exploited the particular properties of these gold "nano-rods" by
manipulating the light pointed at them.
The team members described what they did as adding two "dimensions" to
the three spatial dimensions that discs already have.
They say they were able to introduce a spectral - or colour -
dimension and a polarisation dimension.
The scientists used the nanoparticles to record information in a range
of different colour wavelengths on the same physical disc location.
This is a major improvement over traditional DVDs, which are recorded
in a single colour wavelength with a laser.
Also, the amount of incoming laser light absorbed by the nanoparticles
depends on its polarisation. This allowed the researchers to record
different layers of information at different angles.
The researchers thus refer to the approach as 5-D recording. Previous
research has demonstrated recording techniques based on colour or
polarisation. But this is the first work that shows the integration of
both. As a result, the scientists say they have achieved unprecedented
data density.
Their approach used 10-layer stacks composed of thin glass plates as
the recording medium. If scaled up to a DVD-sized disk, the team would
be able to record 1.6 terabytes - that is, 1,600 gigabytes - or over
300 times the quantity stored on a standard DVD.
Significant improvements could be made by thinning the spacer layers
and using more than two polarisation angles - pushing the limits to 10
terabytes per disc and beyond, the researchers say.
Bit by bit
Recent efforts based on holography have shown that up to 500 Gb could
potentially be stored on standard DVD-sized disks.
Holographic methods take all of the information to be recorded and
encode it in the form of a graph showing how often certain frequencies
arise in it.
That means that the recording process is a complex, all-at-once,
all-or-nothing approach that would be difficult to implement on an
industrial scale.
By contrast, 5-D recording is "bit-by-bit", like current CD and DVD
writing processes in that each piece of information is recorded
sequentially.
That is likely to mean that recording and read speeds would be
comparatively slow, but the approach would be easier to integrate with
existing technology.
"The optical system to record and read 5-D is very similar to the
current DVD system," says James Chon, a co-author on the research.
"Therefore the industrial scale production of the compact system is possible."
Now that the method has been demonstrated in custom-made multi-layer
stacks, the team is working in conjunction with Samsung to develop a
drive that can record and read onto a DVD-sized disc.
Dr Chon says that the material cost of a disc would be less than five
cents (£0.03), but there are a number of advantages in moving to
silver nano-rods that would bring that cost down by a factor of 100.
For optical data storage expert Tom Milster, at the University of
Arizona, the beauty of the approach is in its simplicity.
"It's not just elegant - there are a lot of experiments that are
elegant - it's relatively straightforward," he told BBC News.
For the moment, the equipment needed to write the data would make a
commercial system expensive, but that has not stopped the development
of optical storage solutions in the past.
"For example, Blu-ray player is not a real easy system to realise;
they've got some wonderful optics in there," Dr Milster said. "People
thought that would be pretty difficult to do but others managed to do
it."
http://news.bbc.co.uk/2/hi/science/nature/8060082.stm
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