New density of memory: Image shows microscopic holes cut into the surface of glass with the 'nuclear-strength' laser. Researchers say that the technique could result in an amount of information comparable to that held by the U.S. Library of Congress written in a volume of just one cubic centimetre of material.
Credit: ANU
SYDNEY: Hitting glass with the equivalent energy of a nuclear bomb – but in very short, controlled bursts – could vastly increase computer memory storage capacity, say Australian researchers.
High-powered lasers have been used for several years to bombard transparent materials, such as silicon and sapphire, to create microscopic holes or voids.
Short but intense
As well as their fundamental interest to physicists, the materials – which briefly suffer such extreme temperatures and pressures that tiny, super-hot plasmas form – could create optical memory devices like those used in CDs and DVDs, but with a much higher storage capacity, and in a smaller volume of material.
Now, a team of physicists from the Laser Physics Centre at the Australian National University, in Canberra, have taken the research a step further, by creating a crystalline shell of increased density around the voids, effectively increasingly the density of optical memory.
The researchers tightly focused a laser beam with microscopic lenses and hit a block of glass with very short pulses of light. This heated the glass at a billion billion (1018) degrees per second, but just for a hundred femtoseconds (1/1015 seconds).
"With ultra-short pulses you create a high speed of heating and cooling," said ANU physicist Andrei Rode, who presented the research at the Australian Institute of Physics Congress in Adelaide. "We can also focus the laser more tightly which increases the density of optical memory."
Tiny clouds of plasma
The laser bursts create a tiny cloud of plasma that sends shockwaves through the material, creating many layers of voids that are just 200 nanometres in size.
Blu-ray disks have pits 580 nanometres in size, but within just two layers on the surface of the disk. A block of glass could form a 3-D optical memory device with multiple layers.
"The density of memory we could write is something like the volume of information in the U.S. Library of Congress written in a volume of just one cubic centimetre of material," said Rode. Currently, however, the research is at an early stage and any commercial product is a long way off, he added.
The research also has applications in the manufacture of photonic crystals that can control the flow of light in different media.
In nature, photonic crystals create the play of light in opals and on the scales of iridescent butterfly wings. Photonic crystals could change the way optical fibres direct and control light in telecommunications or broadband internet applications.
Physicist Graham Marshal from the Macquarie University node of CUDOS (Centre for Ultrahigh bandwidth Devices for Optical Systems) said the research was "ground-breaking" and "very nice work."
He said that it brought sci-fi-like concepts such as holographic storage devices used in the movie 2001: A Space Odyssey a step closer.
"DVDs and Blu-ray are currently simple two-layer devices. What these guys are saying is that it might be possible to record data in 3-D with the same kind of precision – or better – as is currently used in a Blu-ray disc, in a block of glass," said Marshal. "If you take data like that from a Blu-ray and stack it up in 3D, then you can store a lot more information in something much smaller than a sugar cube."
