By Lisa Carlin
Researchers at MIT have filled in a piece of the puzzle that could enable the creation of photonic chips on the standard silicon material that forms the basis for most of today’s electronics.
The new component is a “diode for light,” says Caroline Ross, the Toyota Professor of Materials Science and Engineering at MIT. It is analogous to an electronic diode, a device that allows an electric current to flow in one direction but blocks it from going the other way; in this case, it creates a one-way street for light, rather than electricity.
This is essential, Ross explains, because without such a device stray reflections could destabilize the lasers used to produce the optical signals and reduce the efficiency of the transmission. Currently, a discrete device called an isolator is used to perform this function, but the new system would allow this function to be part of the same chip that carries out other signal-processing tasks.
The whole system could be made using standard microchip manufacturing machinery, Ross says. “It simplifies making an all-optical chip,” she says. The design of the circuit can be produced “just like an integrated-circuit person can design a whole microprocessor. Now, you can do an integrated optical circuit.”
This technology could greatly boost the speed of data-transmission systems, for two reasons: First, light travels much faster than electrons. Second, while wires can only carry a single electronic data stream, optical computing enables multiple beams of light, carrying separate streams of data, to pass through a single optical fiber or circuit without interference. “This may be the next generation in terms of speed” for communications systems, Ross says.
Ross’ colleagues in the research included Lionel Kimerling, the Thomas Lord Professor of Materials Science and Engineering, and former students Lei Bi ’11 and Juejun Hu PhD ’09. The work was funded by the National Science Foundation and an Intel fellowship for Bi.