Researchers at IBM published details on a nanophotonic avalanche photodetector that leverages the "avalanche effect" in Germanium, a material currently used in production of microprocessor chips. Analogous to a snow avalanche 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.
IBM said its device can receive optical information signals at 40 Gbps and simultaneously multiply them tenfold. It operates with just a 1.5V voltage supply, 20 times smaller than previous demonstrations. Thus many of these tiny communication devices could potentially be powered by just a small AA-size battery, while traditional avalanche photodetectors require 20-30V power supplies.
"This invention brings the vision of on-chip optical interconnections much closer to reality," said Dr. T.C. Chen, vice president, Science and Technology, 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."
The report of this work, entitled "Reinventing Germanium Avalanche Photodetector for Nanophotonic On-chip Optical Interconnects," by Solomon Assefa, Fengnian Xia, and Yurii Vlasov of IBM's T.J. Watson Research Center in Yorktown Heights, N.Y. is published in the March 2010 issue of the scientific journal Nature.
The Avalanche Photodetector achievement, which is the last in a series of prior reports from IBM Research, is the last piece of the puzzle that completes the development of the "nanophotonics toolbox" of devices necessary to build the on-chip interconnects.
http://www.research.ibm.com/photonics
- In December 2006, IBM scientists demonstrated silicon nanophotonic delay line that was used to buffer over a byte of information encoded in optical pulses - a requirement for building optical buffers for on-chip optical communications.
- In December 2007, IBM scientists announced the development of an ultra-compact silicon electro-optic modulator, which converts electrical signals into the light pulses, a prerequisite for enabling on-chip optical communications.
- In March 2008, IBM scientists announced the world's tiniest nanophotonic switch for "directing traffic" in on-chip optical communications, ensuring that optical messages can be efficiently routed.
- In December 2008, researchers at Intel announced the development of a silicon-based Avalanche Photodetector (APD) that could be used to provide high-capacity optical communications between processor cores. The APD is a light sensor that achieves superior sensitivity by detecting light and amplifying weak signals as light is directed onto silicon.
