Researchers at IBM have made important progress toward creating silicon circuits that communicate using pulses of light rather than electrical signals. This is thanks to a device called nanophotonic avalanche photodetector (NAP), which, as detailed on the journal Nature, is the fastest of its kind and is a major step toward achieving energy-efficient computing that will have significant implications for the future of electronics.
Working on the so-called avalanche effect, which occurs when a photon starts a chain reaction that involves more and more electrons to build up a significant electrical current, the device is part of an ongoing effort by IBM to develop photon-based computing and communication.
"This invention brings the vision of on-chip optical interconnections much closer to reality," T.C. Chen, vice president of science and technology at IBM Research, commented. "With optical communications embedded into the processor chips, the prospect of building power-efficient computer systems with performance at the exaflop [billions of billions of floating point operations per second] level might not be very distant."
The component engineered by IBM is not only by far the fastest of its kind, but also the most efficient on the energy front. It can receive optical information signals at 40 Gb/sec and multiply them tenfold using a mere 1.5V voltage supply — which can be provided by a regular AA-size battery — compared to the 20-30V supplies required by standard photodetectors.
This incredible improvement is the direct result of the transition from standard electronics to photonics. While electronics' performance cannot be pushed over a hard limit of about 100GHz without experiencing unacceptable heating and loss in reliability, photonics can tolerate much higher frequencies and is, researchers suggest, the way to the future.
The NAP is made of silicon and germanium, materials which are already widely used in electronics for microchip production. The device is also fabricated using standard semiconductor manufacturing processes, which is of course essential to cut costs down.
"[Over the past few years] we have developed what you might call a nanophotonic tool kit," Solomon Assefa, who was part of the research group, explained. "We have made most of the devices that we need, such as modulators to modulate the light, waveguides, switches and all the other components to build on-chip interconnects. The NAP is the last piece of the puzzle, which we needed to have one chip send encoded pulses of light, and the next chip receive it and distribute it."
"Now the next step is to continue the development and production of these nanophotonic devices along thin-film transistors. If we put all of this together, we believe that within 10-15 years we will be able to integrate onto the chips with the microprocessors, this photonic interconnect system for networks."
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