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Stanford University Scores Over Super-Fast Computers Working on Light, not Electricity

Infrared light enters this silicon structure from the left. The cut-out patterns, determined by an algorithm, route two different frequencies of this light into the pathways on the right. This is a greatly magnified image of a working device that is about the size of a speck of dust. (Photo: Alexander Piggott)

Light can replace electricity to transmit more data consuming less power and replacing wires, say Stanford University researchers.

Developed by Stanford electrical engineer Jelena Vuckovic tried to miniaturize the proven technology of the Internet, which moves data by beaming photons of light through fiber optic threads.

In a Nature Photonics article whose lead author is Stanford graduate student Alexander Piggott, Vuckovic, a professor of electrical engineering, and her team explain a process that could revolutionize computing by using light instead of electricity to carry data inside computers.

“Optical transport uses far less energy than sending electrons through wires,” Piggott said. “For chip-scale links, light can carry more than 20 times as much data.” The fact that infrared light will pass through silicon the way sunlight shines through glass, they developed the new algorithm.

Theoretically, silicon is transparent to infrared light – the way glass is transparent to visible light. So wires could be replaced by optical interconnects or silicon structures to carry infrared light. But it involves thousands of such linkages for each electronic system and the optical data transport has remained impractical.

Now the Stanford engineers say they have achieved a breakthrough by inventing what they call an inverse design algorithm, in which the engineers specify what the optical circuit should do and the software provides the details of how to fabricate a silicon structure to perform the task.

“We used the algorithm to design a working optical circuit and made several copies in our lab,” Vuckovic said.

Published in Nature Photonics, they said these devices functioned flawlessly despite tiny imperfections. “Our manufacturing processes are not nearly as precise as those at commercial fabrication plants,” Piggott said. “The fact that we could build devices this robust on our equipment tells us that this technology will be easy to mass-produce at state-of-the-art facilities.”

The researchers foresee scores of potential applications for their inverse design algorithm, including high bandwidth optical communications, compact microscopy systems and ultra-secure quantum communications.

The Stanford algorithm designs silicon structures so slender that more than 20 of them could sit side-by-side inside the diameter of a human hair. These silicon interconnects can direct a specific frequency of infrared light to a specific location to replace a wire.

By automating the process of designing optical interconnects, they say the focus should be on the next generation of even faster and far more energy-efficient computers that use light rather than electricity for internal data transport.

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