10-03 :: March 2010
News in Brief
Computer Chips //
Ultra-Fast Device Which Uses Light for Communication
BM (NYSE: IBM) scientists unveiled a significant step towards replacing electrical signals that com-
municate via copper wires between computer chips with tiny silicon circuits that communicate using pulses of light.
The device, called a nanophotonic avalanche pho- todetector, is the fastest of its kind and could enable breakthroughs in energy-efficient computing that can have significant implications for the future of electro- nics.
The IBM device explores the “avalanche effect” in Germanium, a material currently used in production of microprocessor chips. Analogous to a snow ava- lanche on a steep mountain slope, an incoming light pulse initially frees just a few charge carriers which in turn free others until the original signal is amplified many times. Conventional avalanche photodetectors are not able to detect fast optical signals because the avalanche builds slowly.
“This invention brings the vision of on-chip optical interconnections much closer to reality,” said Dr. T.C. Chen, vice president, Science and Technolo- gy, IBM Research. “With optical communications embedded into the processor chips, the prospect of building power-efficient computer systems with performance at the Exaflop level might not be a very distant future.”
Optical microscope photographic image of an array of nanophotonic avalanche photodetectors on a silicon chip. © IBM Research
The avalanche photodetector demonstrated by IBM is the world’s fastest device of its kind. It can receive optical information signals at 40Gbps (billion bits per second) and simultaneously multiply them tenfold. Moreover, the device operates with just a 1.5V vol- tage supply, 20 times smaller than previous demons- trations. Thus many of these tiny communication devices could potentially be powered by just a small AA-size battery, while traditional avalanche photo- detectors require 20-30V power supplies.
Solomon Assefa, Fengnian Xia, and Yurii Vlasov: Rein- venting Germanium Avalanche Photodetector for Nano- photonic On-chip Optical Interconnects, In: Nature, Vol. 464(2010), Number 7285, March 04, 2010, Pages 80-84, DOI:10.1038/nature08813: http://dx.doi.org/10.1038/nature08813