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DVDs are a useful, reliable and relatively cheap way of storing information. Australian researchers have recently developed a technique to massively increase a DVD’s storage capacity.

The shiny surface of a DVD has a whole series of little bumps with flat areas in between. A DVD player has a laser that shines on this surface. Depending on how the light reflects, the DVD player can tell if there’s a bump or not. This pattern is then processed by the player, which converts the information into sounds and pictures. Your favourite movie is reduced to a series of bumps on the surface of a DVD!

The more bumps you can fit on a DVD, the more information you can store on it. One way to do this is to make the bumps smaller. However, until recently, there was a limit to how small the bumps could be.

The bumps are read using lasers, which are beams of light. The smallest spot you can make with a beam of light is around half its wavelength. This limited the size of bumps on a DVD to a few hundred nanometres (billionths of a metre).

A team of Australian researchers has developed a technique that uses two beams of light make a much smaller spot. One of the beams is circular, while the other is a donut shape. A property of light is that sometimes two beams of light can cancel each other out. In this case, the two beams of light overlap, so most of the circular beam is cancelled out. This results in a tiny spot of light, about nine nanometres in diameter.

If this technique can be developed, it would allow DVDs to store information using bumps much smaller in size. Smaller bumps means more bumps, which could allow a storage capacity of up to 1000 terabytes. Given that DVDs currently store 4.7 gigabytes of data, this is 200 000 times more information. You could store more than 10 years of high definition video!

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