PORTLAND, Ore. IBM Research claimed a keystone achievement in on-chip optical communications Wednesday (March 3), saying its 40-gigabit-per-second (Gbps) germanium avalanche photodetector completes what it calls the nanophotonic toolkit.
Capping its multi-year effort by surmounting this final technological hurdle, IBM (Yorktown Heights, N.Y.) now claims to have all the pieces to enable chip-to-chip optical communications and ultimately core-to-core optical communications on the same chip. The remaining development effort to integrate its nanophotonic toolkit into its commercial processors will occur over the rest of the decade, IBM said.
"For several years, IBM has been developing a nanophotonics toolkit for creating optical communications between chips consisting of waveguides, modulators, switches and now the last piece of the puzzle, our nanophotonic avalanche photodetector," said IBM Research Scientist Solomon Assefa. "Now we have everything we need to start integrating photonic communications alongside transistors and make this dream a reality."
Over the last few years, IBM has demonstrated silicon modulators for converting electrical signals into light, a silicon delay line for buffering optical signals plus the waveguides and switches necessary to create a complete chip-to-chip optical bus. With the addition of this nanophotonic avalanche photodetector, IBM claims to have its nanoelectronic ducks in-a-row standing poised to obsolete copper wires in favor of optical communications on and among future chips.
|Optical microscope image of an array of nanophotonic avalanche photodetectors (top) and the silicon waveguides (bottom) directing light to them.|
"We believe that the key to shrinking chips further is leveraging effects at the nanoscale to create both nanophotonic and nanoelectronic devices that work together to make chips cheaper, more power efficient and wider bandwidth by using pulse of light for communications instead of copper wires," Assefa said.
IBM's germanium photodetector multiplies input signals by 10-times using the avalanche effect, yet still achieves 40-Gbps due to its thin film construction, according to IBM. The germainium detector measured just 30 nanometers thick, compared to hundreds of nanometers for competing germanium photodetector designs, enabling its 40 Gbps speed (the avalanche function operates faster for thinner films). Its ultra-thin construction also reduced the normal noise associated with germanium photodetectors by 50 to 70 percent, thereby resurrecting a technology that was once thought to be too noisy for commercialization.
The device also runs off a 1.5 supply voltage, making it perfect for integration on silicon chips compared to traditional avalanche photodetectors which run off 30 volt supplies.
IBM claims that it can fabricate thousands of the photodetectors side-by-side with silicon transistors and integrated silicon waveguides to enable a whole spectrum of on-chip optical communications capabilities for future chips. IBM's long-term plan for integrating silicon photonics with mainstream processors can be viewed on the company's website..