How To Fit 1000 Terabytes On A DVD

How To Fit 1000 Terabytes On A DVD

We live in a world where digital information is exploding. Some 90 per cent of the world’s data was generated in the past two years. The obvious question is: how can we store it all?

Picture: Nature Communications

In Nature Communications today, we, along with Richard Evans from CSIRO, show how we developed a new technique to enable the data capacity of a single DVD to increase from 4.7 gigabytes up to one petabyte (1,000 terabytes). This is equivalent of 10.6 years of compressed high-definition video or 50,000 full high-definition movies.

So how did we manage to achieve such a huge boost in data storage? First, we need to understand how data is stored on optical discs such as CDs and DVDs.

The basics of digital storage

Although optical discs are used to carry software, films, games, and private data, and have great advantages over other recording media in terms of cost, longevity and reliability, their low data storage capacity is their major limiting factor.

Picture: Adam Foster/Codefor

The operation of optical data storage is rather simple. When you burn a CD, for example, the information is transformed to strings of binary digits (0s and 1s, also called bits). Each bit is then laser “burned” into the disc, using a single beam of light, in the form of dots.

The storage capacity of optical discs is mainly limited by the physical dimensions of the dots. But as there’s a limit to the size of the disc as well as the size of the dots, many current methods of data storage, such as DVDs and Blu-ray discs, continue to have low level storage density.

To get around this, we had to look at light’s fundamental laws.

Circumnavigating Abbe’s limit

In 1873, German physicist Ernst Abbe published a law that limits the width of light beams.

On the basis of this law, the diameter of a spot of light, obtained by focusing a light beam through a lens, cannot be smaller than half its wavelength – around 500 nanometres (500 billionths of a metre) for visible light.

Picture: Wikimedia Commons

And while this law plays a huge role in modern optical microscopy, it also sets up a barrier for any efforts from researchers to produce extremely small dots – in the nanometre region – to use as binary bits.

In our study, we showed how to break this fundamental limit by using a two-light-beam method, with different colours, for recording onto discs instead of the conventional single-light-beam method.

Both beams must abide by Abbe’s law, so they cannot produce smaller dots individually. But we gave the two beams different functions:

  • The first beam (red, in the figure right) has a round shape, and is used to activate the recording. We called it the writing beam
  • The second beam – the purple donut-shape – plays an anti-recording function, inhibiting the function of the writing beam

The two beams were then overlapped. As the second beam cancelled out the first in its donut ring, the recording process was tightly confined to the centre of the writing beam.

Picture: Nature Communications

This new technique produces an effective focal spot of nine nanometres – or one ten thousandth the diameter of a human hair.

The technique, in practical terms

Our work will greatly impact the development of super-compact devices as well as nanoscience and nanotechnology research.

The exceptional penetration feature of light beams allow for 3D recording or fabrication, which can dramatically increase the data storage – the number of dots – on a single optical device.

The technique is also cost-effective and portable, as only conventional optical and laser elements are use, and allows for the development of optical data storage with long life and low energy consumption, which could be an ideal platform for a Big Data centre.

As the rate of information generated worldwide continues to accelerate, the aim of more storage capacity in compact devices will continue. Our breakthrough has put that target within our reach.

Min Gu is a Laureate Fellow of the Australian Research Council. Yaoyu Cao and Zongsong Gan do not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article. They also have no relevant affiliations.
The ConversationThis article was originally published at The Conversation. Read the original article.


    • you’ll get it when you’re more positive about scientific advances and more patient about how long cutting edge developments take to get to consumers.

  • Those clever bastards at CSRIO, thats brilliant. Reminds me of the old magneto-optical drives that used a laser to enable writing a bit smaller than what was exposed to the magnetic field (by heating it).

  • Wow & flutter – caused by misalignment of the centre hole on a vinyl LP. How much misalignment, every time you throw a DVD on a spindle? Dust & fingerprints on the surface? Wobble from an unbalanced disc?
    Heck, even if you make it a sealed unit like a HDD you’re going to lose a lot of that surface to Error Correction. And we haven’t even discussed Access Time for finding a single track 9 nanometres wide…

    • They probably said similar things when the best storage we had was a room-sized 10MB hard drive

  • Good on you CSIRO gurus.

    Hope you make another shitload of money for Australia from the patent royalties.

  • I’m trying to think of a way this could be used for evil.. And i’m coming up short..


    • You can use it to reduce the cost of storing the data intercepted by the PRISM… 😉

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