Researchers at the California Institute of Technology and the University of California, San Diego have developed a silicon-based optical waveguide that could prove to be an instrumental component in building low-cost, all-optical networks in the future.
The device resembles an electrical diode, at least in that it will allow light to move in one direction while blocking any light from moving in the opposite direction. Such isolation minimizes interference that would otherwise take place among multiple sources of light in a tightly packed optical component.
"One-way flow is very important for the integration of photonic components on the same chip," said Liang Feng, a CalTech researcher and lead author of a paper describing the work in Friday's edition of the journal Science.
This work is a crucial step in building silicon chips with optical components, said Nasser Peyghambarian, a professor of optical sciences at the University of Arizona in Tucson, who was not involved in the project.
Such chips could be used in networking hardware such as routers and switches. While today's long-distance networks transmit data in photon streams over fiber-optic cables, the switching and routing still needs to be done electronically. So data traffic has to be converted from light to electrons and back to light again.
"When you convert information from optics, you have some data loss," Feng said. Packets that are dropped need to be retransmitted, which lowers the overall efficiency of the system. "Doing everything photonically, you get rid of this loss. It's more energy-efficient and more straightforward."
"In order to get to low-cost and low-energy consumption, this conversion between optics and electronics has to be minimized as much as possible," Arizona's Peyghambarian said.
The Caltech and UCSD researchers were not the first to create this type of waveguide, or isolator. But previous prototypes from others were built with more esoteric materials, which would not lend themselves to low-cost mass production. By fashioning their device from silicon, the researchers have set the stage for incorporating this technology into chips that can be produced at low cost and in high volumes.
"It is a great technology that they have produced," Peyghambarian said.
The work also helps set the stage for optical computing, or computers that process data captured in photons in much the same way today's computers manipulate data as electrons. Such computers, should they ever be made, would still be decades away, Peyghambarian said.
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