Light can transmit more data while consuming far less power than electricity, and an engineering feat brings optical data transport closer to replacing wires.
In computers today, data is pushed through wires as a stream of electrons. That takes a lot of power, which helps explain why laptops get so warm.
“Several years ago, my colleague David Miller carefully analyzed power consumption in computers, and the results were striking,” said Vuckovic, referring to David Miller, the W.M. Keck Foundation Professor of Electrical Engineering. “Up to 80 percent of the microprocessor power is consumed by sending data over the wires – so-called interconnects.”
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 making it practical to use light instead of electricity to carry data inside computers.
In essence, the Stanford engineers want to miniaturize the proven technology of the Internet, which moves data by beaming photons of light through fiber optic threads.
“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.”
Theoretically, this is doable because silicon is transparent to infrared light – the way glass is transparent to visible light. So wires could be replaced by optical interconnects: silicon structures designed to carry infrared light.
But so far, engineers have had to design optical interconnects one at a time. Given that thousands of such linkages are needed for each electronic system, optical data transport has remained impractical.
Now the Stanford engineers believe they’ve broken that bottleneck by inventing what they call an inverse design algorithm.
It works as the name suggests: the engineers specify what they want the optical circuit to 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.
In addition to Piggott, the research team included former graduate student Jesse Lu (now at Google,) graduate student Jan Petykiewicz and postdoctoral scholars Thomas Babinec and Konstantinos Lagoudakis. As they reported in Nature Photonics, the 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 envision many other potential applications for their inverse design algorithm, including high bandwidth optical communications, compact microscopy systems and ultra-secure quantum communications.