Light could help make more efficient computers

Researchers have developed a series of novel devices to make computing just a tiny bit more efficient.

Last year, Northeastern University assistant professor of physics, Swastik Kar, and colleague Yung Joon Jung, an associate professor in the Department of Mechanical and Industrial Engineering, combined their expertise-Kar's in graphene, a carbon-based material known for its strength and conductivity, and Jung's in the mechanics of carbon nanotubes, which are nanometer sized rolled up sheets of graphene-to unearth a physical phenomenon that could usher in a new wave of highly efficient electronics.

They discovered that light-induced electrical currents rise much more sharply at the intersection of carbon nanotubes and silicon, compared to the intersection of silicon and a metal, as in traditional photodiode devices.

Kar said that the sharp rise helps them design devices that can be turned on and off using light.

This finding has major implications for performing computations, which, in simple terms, also rely on a series of on off switches.

In the new paper, the team presents three such new devices. The first is a so called AND gate, which requires both an electronic and an optical input to generate an output. This switch only triggers if both elements are engaged.

The second device, an OR gate, can generate an output if either of two optical sensors is engaged. This same configuration can also be used to convert digital signals into analog ones, an important capability for actions such as turning the digital content of an MP3 file into actual music.

Finally, Kar and Jung also built a device that works like the front-end of a camera sensor. It consists of 250,000 miniature devices assembled over a centimeter by centimeter surface. While this device would require more integration to be fully viable, it allowed the team to test the reproducibility of their assembly process.

The research has been published in the journal Nature Photonics.