Compact Memory
Light-sensitive ­material could hold multiple bits of data in the same area.

Source: “Five-dimensional optical recording mediated by surface plasmons in gold nanorods”
James W. M. Chon et al.
Nature 459: 410-413

Results: Researchers at Swinburne University of Technology in Australia have developed a light-responsive material that can store data at a density of over 1,000 gigabytes per cubic centimeter. It is made up of 10 layers of gold nanoparticles that change shape depending on the color and polarization of light shined on them, a property that makes it possible to store more than one bit of information in a given region of the material.

Why it matters: The material can store far more data than Blu-ray discs, the highest-­density optical storage technology on the market today. Each of those discs can store only 50 gigabytes (about 4.6 gigabytes per square centimeter).

Methods: To store multiple bits of information in a single region, researchers irradiate the region with laser light in different combinations of colors and polarizations. Each combination creates a distinct change in the gold nanoparticles that can be read by shining another laser on the region and measuring the reflected light. The researchers engineered particles that respond to yellow, blue, and green light, exploiting the fact that nanoparticles absorb different colors depending on their size. To ensure that the particles respond to different polarizations, the researchers made them rod-shaped. When the light’s polarization is aligned with the rods’ long axis, they absorb more light, causing the rods to change shape more than if the polarization is not thus aligned. Data can be written separately to different layers of the material, further increasing the amount of data that can be stored in a given area.

Next steps: The researchers will work with Samsung and other companies to engineer data-storage devices based on the new material.