IBM researchers are one step closer to building a microprocessor that transfers data with light instead of electricity, a technique that could one day boost computing speed while saving power.

While most chip designers seek ways to speed up their processors, the IBM researchers said Thursday they have found a way to slow theirs down. That is important because photonic chips have always faced the criticism they could transmit data quickly, but could not store it.

Now, the IBM research shows a way to buffer photonic data by routing light signals through an optical delay line, forcing each photon to travel through up to 100 tiny rings instead of making a beeline for the other side of the chip. Even better, the researchers say they can manufacture the devices cheaply, since they created the new "micro-ring resonators" using standard silicon CMOS (complementary metal oxide semiconductor) fabrication tools.

IBM performed this research with funding from the U.S. Department of Defense's Defense Advanced Research Projects Agency (DARPA), and will publish the results in the current issue of the journal Nature Photonics.

Many of today's PCs already have sufficient computing power in their microprocessors, said T.C. Chen, the vice president of science and technology for IBM Research. A more challenging bottleneck is keeping those chips fed with data. IBM's new research could finally clear that hurdle, he said.

Still, they face a stiff challenge in scaling up the technique to make functioning chips. The current model can briefly store 10 bits of optical data in an area of 0.03 square millimeters. That is better than any previous model, but the researchers would have to integrate hundreds of the devices onto a single chip in order to build a photonic processor.

Analysts estimate that optical silicon technology such as IBM's new method or a similar design from Intel Corp. will not reach maturity for five to 10 years.

"This is only a building-block technology," said Peter Middleton, principal research analyst at Gartner Inc. "It will have to be combined with techniques to inject a light source onto the chip, distribute it on-chip, and convert it back to an electrical signal at the receiver site."

If IBM engineers can design such a system, and hold manufacturing costs down, then hybrid electronic/optical systems could make a significant impact, he said. Chip designers face a growing challenge with power consumption and latency issues in traditional interconnects. IBM's new research could help solve such puzzles by linking a large number of interconnected processor cores on a single chip, Middleton said.

The first application for such a chip would be supercomputing, followed by high-performance, general purpose processors from companies such as Intel Corp., Advanced Micro Devices Inc., Freescale Semiconductor Inc. and IBM itself.