Diamond is a promising material for data storage, and now scientists have demonstrated a new way to cram even more data onto it, down to a single atom. The technique bypasses a physical limit by writing data to the same spots in different-colored light.
Diamond has great potential as a data storage medium – recent developments have produced 2-inch (5-cm) wafers of the stuff that can store the equivalent of a billion Blu-Ray discs. Intriguingly, it works not by writing data to the diamond itself but to tiny nitrogen defects in the material. These defects can absorb light, earning them the name “color centers.”
Usually, optical memory technologies have a hard limit to how fine they can write data – after all, there’s a minimum diameter that a laser beam can be focused to. Known as the diffraction limit, this scales with the wavelength of light used.
“You cannot use a beam like this to write with resolution smaller than the diffraction limit because if you displace the beam less than that, you would impact what you already wrote,” said Tom Delord, co-author of the study. “So normally, optical memories increase storage capacity by making the wavelength shorter (shifting to the blue), which is why we have ‘Blu-ray’ technology.”
But for the new study, researchers at the City University of New York (CUNY) found a way to bypass the diffraction limit. The trick is to use different wavelengths of light to write data to color centers that are closer together than the diffraction limit allows – you might not be able to put two “greens” side-by-side, for example, but if you alternate between, say, green, red and blue, you could theoretically store three times as much data in one region than if you used a single color.
“What we did was control the electrical charge of these color centers very precisely using a narrow-band laser and cryogenic conditions,” said Delord. “This new approach allowed us to essentially write and read tiny bits of data at a much finer level than previously possible, down to a single atom.”
In tests, the team demonstrated that the technique could imprint 12 different images in the same spot at different frequencies, achieving a data density of 25 GB per square inch (6.4 sq cm). For comparison, that’s how much a standard single-layer Blu-Ray disc holds across its whole surface. As an added bonus, this technique is reversible, so data can be written, erased and rewritten essentially as many times as needed.
With further work, the team says that this technique could be applied to other materials and hopefully, at room temperature rather than cryogenic conditions.
The research was published in the journal Nature Nanotechnology.
Source: CUNY