Most data storage devices we currently use are, at their core, two-dimensional. Sure, a hard drive might have multiple platters, but the data storage takes place on a flat surface. Even an optical drive is effectively a single surface that holds data. At the City College of New York, they are experimenting with storing data in three dimensions using lab-grown diamonds and LASERs.
Usually, diamonds that have few flaws are more valuable. But in this application, the researchers exploit the flaws to store information. Optical memory that uses a volume instead of a surface isn’t exactly new. However, it is difficult to use these techniques in a way that is rewritable.
Diamonds are a crystalline structure of carbon atoms. Sometimes, though, a carbon atom is missing from the structure. That’s a vacancy. Another defect is when a nitrogen atom replaces a carbon atom. Sometimes a vacancy occurs next to a rogue nitrogen atom and that causes an NV (nitrogen vacancy) center.
It turns out these NV centers are exploitable in several ways ranging from magnetic resonance detection to quantum mechanics experiments. The NV centers can trap an electron, but can also be forced to release a trapped electron. This allows you to treat an NV center with or without an electron as a binary one or zero.
A green LASER can inject an electron into an NV center. A red LASER at low power can determine if an electron is present. At higher powers, the red LASER will eject an electron from an NV center if it is present. If the diamond is in total darkness, the memory state will persevere “virtually forever” according to the researchers (we guess diamonds really are forever).
Of course, the LASER beams are larger than the single-atom defects, but the researchers actually use that to their advantage. By controlling the duration of the LASER pulse, a particular number of NV centers can be charged. That allows a single pulse to store or read multiple bits of data. For example, if the volume contained four NV centers, the volume could represent two bits of information. Since the diamonds are created in a lab, the concentration of NV centers is deterministic.
Currently, the device can store data at a density that exceeds a DVD by about 100 times. However, they are working on ways to get even more dense storage.
Photo Credit: [Siddharth Dhomkar] and [Jacob Henshaw] CC BY-ND