In this story, Technology Review says that Italian researchers found a way to reach storage densities as high as a trillion bits per square inch for rewritable devices.
They used a near-field scanning optical microscope to aim a nanoscale spot of polarized blue light on a polymer. The light caused the polymer molecules it hit to change shape and line up. Aligned and non-aligned molecules could represent the 1s and 0s of digital information.
The reversible process could eventually be used in rewritable data storage devices that could hold more than a trillion bits per square inch, according to the researchers. That's about 2,000 times more than today's DVDs, which hold 537 million bits per square inch.
The researchers used the method to scribe 100-nanometer lines into a polymer film. The method could enable marks as small as 10 nanometers. The medium retained data for several months, and is likely to remain stable long enough for practical applications, according to the researchers.
However, this is not a practical method as of today, because they only can write 100 bits per second. The Italian researchers are working hard to improve this speed and expect real devices in a two to five years timeframe.
The work of these researchers has been published by Applied Physics Letters on May 12, 2003 (Volume 82, Issue 19, pp. 3313-3315).
Here is the abstract, "Optical nanowriting on azobenzene side-chain polymethacrylate thin films by near-field scanning optical microscopy."
Optical writing and subsequent reading of information on thin films of azobenzene side-chain polymethacrylates on the 100-nm scale are demonstrated by near-field scanning optical microscopy (NSOM) with polarization control. Polarized blue light at 488 nm coupled to the NSOM aperture probe activates trans-cis-trans isomerization cycles of the side chains, causing their alignment and thus locally inducing optical birefringence. Red light at 690 nm with modulated polarization is coupled to the same aperture and used to detect optical anisotropy on the local scale. Lines of width on the 100-nm scale were optically inscribed and detected even with no concurrent topographic modification.
Sources: Technology Review, July 30, 2003; Applied Physics Letters, May 12, 2003
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