March 2008 - Issue #1
Future CD's to be a digital Aladdin's cave
Story by David Adams
Imagine being able to put your entire DVD collection on a single disc. And not just your collection, but also that of your family, friends and neighbours ... the contents, in fact, of as many as 200,000 DVDs.
It sounds a stretch of imagination, but this is the aim of Professor Min Gu and his team at Swinburne University of Technology's Centre for Micro-Photonics.
They are three years into a fiveyear project that is looking at how nanotechnology - particularly the use of nanoscopic particles - can be used to exponentially increase the amount of information contained on a single disc.
Their ultimate aim is to be able to include as much as a petabyte (PB) - 1015 or one quadrillion bytes - of data on a single disc, an amount 20,000 times greater than the amount of data currently able to be stored on a Blu-ray Disc, which is a high-density optical disc format. "The idea is to incorporate nanostructured material and to increase the data capacity without necessarily increasing the size of the CD or DVD disc," says Professor Gu, who is director of the Centre for Micro-Photonics and leading the $1 million project.
Funded by a grant from the Australian Research Council, the project aims to create these 'next generation' discs using a number of different techniques, the first of which involves dramatically expanding the number of layers in which data can be stored.
Dr James Chon, a senior lecturer at the centre and one of the researchers involved in the project, explains that while a typical CD is about 1.2 millimetres thick, the information recorded on it using what is now standard technology takes up less than a micron - one thousandth of a millimetre - of the CD's thickness.
"The idea is to incorporate nanostructured material and to increase the data capacity without necessarily increasing the size of the CD or DVD disc."
Professor Min Gu
"But these are just proof-of-principle experiments," Dr Chon says. "If we wanted to, we could go up to 200 and 300 layers." Alongside the use of layering techniques, the project is also exploring how nanotechnology can enable data to be stored in two further 'dimensions' in addition to the three spatial dimensions already used.
The first is the spectral - or color - dimension. While CDs and DVDs are currently recorded in a single-colour wavelength using a laser, the project is examining how, thanks to the fact that nanoparticles react to light according to their shape, differently shaped nanoparticles can be inserted onto a disc to allow information to be recorded in a range of different colour wavelengths on the same physical disc location.
The second of the additional 'dimensions' can be created using polarisation. This uses the electric field that is present in the light waves being employed to write information on a disc. When the light waves are projected onto the disc, the direction of the electric field contained within them will align particular nanoparticles and allow data to be stored on them. Altering the direction of the incoming light wave, and the electric field within, different nanoparticles will be aligned and so allow more data to be stored.
"That polarisation can be rotated 360 degrees," explains Dr Chon. "So, for example, if you were to record at zero degree polarisation, you could also, on top of that, record another layer of information at 90 degrees polarisation and they will not interfere with each other.
" While specially manufactured spherical semi-conductor nanoparticles can be used to record in the three spatial dimensions, plus the spectral dimension, to provide the added ability to store data in a fifth dimension, metallic nanorods - which measure up to 60 nanometres (a millionth of a millimetre) - are also being used, thanks to their sensitivity to polarisation.
Although many issues, such as the speed at which the discs can be written on, are yet to be resolved, the researchers - who have already signed an agreement with electronics manufacturer Samsung - say the discs would have immediate applications in a range of fields and could be in commercial use within 10 years.
Professor Richard Evans, a senior principal research scientist at CSIRO's Molecular and Health Technologies Division and an adjunct professor at the Centre for Micro-Photonics, says that as well as being a great means of storing extremely large medical files, such as MRI scans, such storage capacity would also prove a boon in the financial world as well as within military and security arenas.
Professor Evans, who has provided components for some of the specially manufactured nanoparticles for the project, says there is also great potential for the technology within homes, particularly given the growing trend for people to make digital records of so much of their lives. "People are becoming digital 'completists' in their lives," he says. "They want to document basically everything ... and people will make use of whatever data space you