Today’s computer chips are chunks of silicon that use electrical pulses to crunch data. But IBM researchers are now making chips for tomorrow: chunks of silicon that also contain pathways for light pulses.
These optical circuits can exchange information with the conventional, electronic circuits in the same chip. This could transport data inside a computer significantly faster, because light signals can transport larger quantities of data at higher speeds than conventional copper electrical wiring can. A chip could use its optical—photonic—circuits for high-speed input and output.
“We need faster ways to shuttle information around,” says Solomon Assefa, a member of the research team at IBM’s Watson Research Center in Yorktown Heights, New York. “Our main motivation is to build, in five years or so, exascale systems that will be 1,000 times faster than what we have now.”
Today’s supercomputers are dubbed “petascale” because their power is measured in petaflops, or quadrillions of floating-point operations per second. The U.S. Department of Energy has urged the development of machines capable of exaflops—quintillions of operations per second—to enable more powerful simulation-based research into climate change and renewable and nuclear energy.
Over the past seven years, IBM’s researchers have developed a chain of individual silicon components that together can convert a chip’s electrical signals into light signals and back again. Now they’ve found a way to build all of those components on the same chip without inhibiting the transistors’ performance, using the standard complementary metal-oxide semiconductor (CMOS) techniques used to build processors and other chips today.
Now that this goal has been achieved in the lab, says Assefa, “the next step is to transfer this to a commercial fab, like those making chips today.” Although the technology is not expected to be market-ready for around five years, IBM is keen to test its techniques on the production equipment for which they are designed.
This is a significant advance, says Bahram Jalali, a professor of electrical engineering at the University of California, Los Angeles, who helped kick-start silicon photonics when he developed the first silicon laser in 2004. “Integration with CMOS is a very difficult thing that has been a vision of many in the field for some time,” he says.
Other companies have been developing silicon photonics as well. Earlier this year, Intel unveiled a collection of dedicated photonic chips that can be used to carry data between conventional electronic chips. Caltech spinoff Luxtera puts photonic components on a silicon wafer after the electronic silicon components have been completed.