Researchers at Swinburne University of Technology explain how they invented a clever way to pack a lot more data on optical media–as much as 1,000 terabytes on a DVD that today holds just 4.7 gigabytes.
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.
This new technique produces an effective focal spot of nine nanometres – or one ten thousandth the diameter of a human hair.
It is not quite Charles Stross’ vision of memory diamonds, but it’s good to see research progressing on how we’re going to store all that 4K porn.