IBM researchers invent device that uses light to help computer chips communicate

Summary:IBM scientists on Wednesday announced the development of a device that uses light, instead of copper wires, to allow computer chips to communicate.

IBM scientists on Wednesday announced the development of a device that uses light, instead of copper wires, to allow computer chips to communicate.

The advancement is a step toward replacing the electrical signals that computer chips use to talk to each other in pursuit of more energy-efficient computing.

Called a nanophotonic avalanche photodetector, the device is the fastest of its kind and has "significant implications" for the future of electronics, IBM says.

"This invention brings the vision of on-chip optical interconnections much closer to reality," said T.C. Chen, IBM Research vice president of science and technology, in a statement. "With optical communications embedded into the processor chips, the prospect of building power-efficient computer systems with performance at the Exaflop level might not be a very distant future."

They key to the device is a process called the "avalanche effect" in germanium, a material used to make microprocessor chips. Like a mountain avalanche, an incoming light pulse frees a few charge carriers that, in turn, free others until the original signal is amplified many times.

IBM says current avalanche photodetectors can't detect fast optical signals because the avalanche builds too slowly.

IBM's device, on the other hand, is fast enough to receive optical information signals at 40Gbps and simultaneously multiply them tenfold.

The avalanche multiplication takes place within a few tens of nanometers, allowing multiplication noise to be suppressed by 50 to 70 percent compared to existing devices.

"This dramatic improvement in performance is the result of manipulating the optical and electrical properties at the scale of just a few tens of atoms to achieve performance well beyond accepted boundaries," said lead author Solomon Assefa in a statement. "These tiny devices are capable of detecting very weak pulses of light and amplifying them with unprecedented bandwidth and minimal addition of unwanted noise."

Made of silicon and germanium using standard chip manufacturing processes, the device operates with only a 1.5V voltage supply, which the company says is 20 times smaller than previously demonstrated.

That's important because that allows an array of these photodetectors to be powered by a small AA-size battery, rather than the 20V to 30V power supplies required by existing devices.

Here's a video:

Their research was published in the March 2010 issue of the journal Nature.

This post was originally published on

Topics: Innovation


Andrew Nusca is a former writer-editor for ZDNet and contributor to CNET. He is also the former editor of SmartPlanet, ZDNet's sister site about innovation. He writes about business, technology and design now but used to cover finance, fashion and culture. He was an intern at Money, Men's Vogue, Popular Mechanics and the New York Daily Ne... Full Bio

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