Researchers in Australia have demonstrated a new storage technology that could potentially allow 10 terabytes to be stored on a DVD-sized disc.

"To put that in perspective, that's the… capacity of 2,000 DVDs," said Richard Evans, a research scientist at the Commonwealth Scientific and Industrial Research Organisation, in an online news conference organized by the Australian Media Centre.

How it works

Each layer contains extremely tiny gold particles called "nanorods," said James Chon, co-author of the article, at the news conference. Each nanorod is about 1/30th to 1/70th the size of the rod-shaped bacterium that causes anthrax.

When a nanorod is hit by a laser of the right colour, it melts into a more spherical particle that can no longer be "seen" when the layer is read.

The reading laser only interacts with a single layer at the laser focus due to the reading technique used, Chon said in an email. That means multiple nanorod layers can be stacked between layers of transparent spacers to create a three-dimensional storage material, and the laser will not interfere with the layers that are not being read.

But the data isn't just stored in three dimensional space. It is also stored using different colours and different polarizations of light — the two other "dimensions." Polarization refers to the direction in which light waves are oscillating. The direction can be rotated within 360 degrees using a filter.

Nanorods of different sizes respond to different colours of light. Nanorods of different orientations respond to different polarizations of light. Nanorods hit with the wrong colour or polarization are unresponsive and therefore "invisible."

Because of that, said Richard Evans, an engineering professor, "using three colours and three polarizations, you can get nine data sets written in the same exact spot."

The researchers tested their technology by writing 18 images on a single slide using three layers, three different colours and two different polarizations of light.

Evans, who is also an engineering professor at Swinburne University of Technology in Melbourne, Australia,  was discussing the results of a study conducted by three other Swinburne researchers — Peter Zijlstra, James Chon and Min Gu — and published in Thursday's edition of Nature. Evans, who also researches optical data storage, proofread the paper.

The new technology, backed by Samsung Electronics, is expected to be commercially available within five or 10 years, said a news release from the university.

The technique involves storing information in thin layers, as CD, DVD and Blu-Ray discs do, with spots or bits of data written and read by a laser.

Chon said the next steps will be to:

  • Test the technology on an actual DVD-sized disc.
  • Develop an optical drive that will work with it.
  • Try different nanorod materials. For example, he is interested in trying silver nanorods, as they are cheaper than gold and allow the use of shorter light wavelengths, such as blue and violet.

A DVD with a single layer can currently store 4.7 gigabytes (about 5/1000ths of a terabyte), using a laser to read tiny spots of data stored close together. Reducing the size of the data spots and the light beam can increase the disc capacity. That is how Blu-Ray discs can hold five times more than DVDs on a single layer.

However, the capacity of such two-dimensional technologies is ultimately limited by the fact that the laws of physics limit the smallest spot size that it is possible to focus visible light to, Chon said.

Holographic competition

Another method of three-dimensional storage that could potentially boost storage capacities exponentially is holographic storage. GE Global Research, the technology development arm of the General Electric Company, announced in April that it had validated holographic storage technology that could store 500 gigabytes on a DVD-sized disc.

Instead of storing data as individual spots, holography uses a light beam containing data and a second light beam called a "reference beam" to create interference patterns in the storage medium. When the reference beam is shone on the storage medium, those patterns serve as a "mould" that diffracts light in a way that reproduces the original data.

Evans argued that it will be easier to make the 5D storage technology backward compatible with existing Blu-Ray and DVD technology than to make holographic technology backward compatible because holographic technology is so different from CD and DVD technology.

However, GE has said its hardware and formats are so similar to current optical storage technology that the micro-holographic players will enable consumers to play back their CDs and DVDs.