Stanciu et al., Physical Review Letters

Right, left, left.
Artist's impression of how laser pulses could replace conventional data transfers to magnetic disks by reversing the spin--and therefore the polarity--of their photons.

Lighting a Fire Under Hard Drives

In the race to make computers more powerful, magnets may be out and lasers may be in. Ultra-rapid pulses of polarized light fired from lasers, new tests show, can outperform conventional magnetic data writers by as much as two orders of magnitude. The technology could form the foundation of a new generation of computers that link lasers to their hard drives.

Long gone are the days when computers were required only to make mathematical calculations. Even modest desktop models are now expected to handle streaming audio and video from multiple Web sites simultaneously, for example. Those functions require huge amounts of data to be transferred quickly to and from the hard drive. But current data-processing systems, which use magnets to write and read the binary code that constitutes computer language, can only work so fast. Some users' needs have begun to bump up against the limitations of this technology. If computers are to become faster, they'll require a different data-transfer system, and the awesome promise of quantum computing remains years away.

Researchers at Radboud University Nijmegen in the Netherlands think they've found another candidate. In laboratory experiments, they used laser light to write data to a magnetic hard drive at very high speeds. The technique works because the photons transmitted by the laser actually carry angular momentum, allowing them to interact with the hard drive. Also, each laser pulse heats a tiny space on the disk just enough to make changing its polarity--thereby storing a bit of data--a little easier. The key is reversing the polarity of the laser pulses, which can produce the equivalent of either a 1 or a 0 of binary code on the disk storage medium.

The researchers managed to transfer data at intervals of about 40 femtoseconds, or quadrillionths of a second, about 100 times faster than conventional magnetic transfers, the researchers report in a paper accepted for publication by Physical Review Letters. One drawback is that the footprint of the laser pulse on the disk is about 5 microns wide, which is considerably larger than the footprint produced by existing data-transfer systems. But physics doctoral candidate and co-author Daniel Stanciu says the team is working on improvements in the technology that should reduce the footprint's size to about 10 nanometers, and he expects to see a working prototype within a decade.

"This is one of the most exciting stories in magnetics," says physicist Julius Hohlfeld of Seagate Research in Pittsburgh, Pennsylvania. Lots of other researchers have tried to employ polarized laser light to write data, he says, but everyone failed because the magnetic alloys they used for the storage medium did not work. But the disk made of gadolinium, iron, and cobalt that Stanciu's team used has succeeded. The next challenge, Hohlfeld says, will be to find a relatively cheap laser technology that can fire pulses lasting less than 100 femtoseconds.

Posted in Math