Over recent years, there has been an increasing demand for higher-capacity storage devices, which is met with the advancements in optical data storage technologies. Known for their exceptional hardness and durability, diamonds have long been considered a potential candidate for high-density data storage. In a new study, experts discovered a way to significantly increase the capacity of diamonds by circumventing the diffraction limit.
Limitations in Optical Data Storage
In optical memory technology, the capacity of devices is defined by the "diffraction limit," or the minimum diameter that a beam can be focused to. It approximately scales as half the light beam wavelength.
A beam like that cannot be used in writing with a resolution smaller than the diffraction limit because displacing the shaft less than that would impact what was already written. In typical cases, optical memories increase storage capacity by making the wavelength shorter in a technology known as "Blu-ray."
Blu-Ray technology uses a blue laser with a shorter wavelength than red, allowing more bits of information to be written in the same space. Blue strands are finer and enable the user to print four in the same space needed for two red strands, increasing storage density per area.
Breakthrough in Data Storage
A team of scientists demonstrated the possibility of processing data in multiple colors within different diffraction limits. Physicists Richard G. Monge and Tom Delord from The City College of New York have demonstrated a new way to store more diamond data on a single atom. They made it possible by multiplexing the storage in the spectral domain to bypass the diamond's physical limit.
The CCNY researchers focused on a tiny element called "color centers" found in diamonds and similar materials. These elements are atomic defects that can absorb light and serve as a platform for quantum technologies. Using a narrow-band laser and cryogenic conditions, the scientists precisely controlled the electrical charge of these color centers. This new approach enabled them to write and read tiny bits of data at a much finer level than previously thought.
Using a slightly different-colored laser, experts can now store different information in different atoms in the same microscopic spots, such as placing many different images in the same place in the diamond. The researchers are confident that if this approach is applied to other materials or at room temperature, it can find its way to computing applications requiring high-capacity storage.
What makes CCNY's optical storage approach different from others is its circumventing the diffraction limit by exploiting the slight changes in wavelength. Such changes exist between color centers separated by less than the diffraction limit.
The researchers tried to tune the beam to slightly shifted wavelengths, allowing them to keep it at the exact physical location. However, it interacted with different color centers to change their charges selectively, using sub-diffraction resolution to write data.
This new approach is also reversible, which means the user can write, erase, and rewrite data an infinite number of times. Other optical storage devices can also do this, which is unusual, especially in high spatial resolution. In a Blu-ray disc, for example, a movie can be stored on the device, but it cannot be erased and written with another.
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