Developing a new use for the material that’s already the foundation of the computer chip industry, Intel Corp. researchers have built a continuously shining silicon laser that could drive down the cost of optical networking.
Such a laser could make high-bandwidth, light-based communication feasible for not only the connections between computers but also the links between components inside PCs. It also could slash the cost of lasers used in defense, medicine and other industries.
Just a few years ago, few experts thought silicon could be used to build a laser, said Mario Paniccia, director of Intel’s photonics lab. It tends to absorb light energy, dissipating it as heat rather than amplifying it like lasers built with more exotic materials.
“This is a fundamental breakthrough,” said Paniccia, a co-author of the Intel study, which was to be published in the journal Nature on Thursday. “It’s one of those things that’s a game changer. You’re doing something in silicon that couldn’t be done before.”
If the research continues on track, the devices could be made in the same plants now used to build microprocessor and memory chips, thereby helping companies like Intel further leverage their multibillion-dollar manufacturing investments.
Laser beams are usually created by using a blast of electricity or light to boost the energy levels of electrons in atoms of polished crystal rods, semiconductors, gases or vapors. Then the electrons fall back, and photons, the basic element of light, are released. The photons are then bounced back and forth before they’re beamed out as concentrated light.
The basic process doesn’t work with silicon because of its physical qualities. Instead, researchers focused on a weak but precise scattering of photons called the Raman effect, which occurs when silicon is stimulated by a light source.
It turns out silicon is a good material for Raman lasers, which are already being used in the fiber of long-haul telecommunications networks. Previous research found that with silicon, the effect is 10,000 times stronger than in the glass fiber. That means the effect is stronger at shorter distances.
The paper published Thursday is the second in less than a month from Intel researchers. In January, they announced that they had built an all-silicon laser, by etching channels into silicon that amplify pumped-in light. But there was a problem: after a time, the laser beam stopped. Researchers worked around the problem by developing a pulsed laser — and the pulsing unfortunately made it impractical for most uses.
“Basically, it’s a show stopper,” Paniccia said.
Further study revealed that the light pumped into the laser cavity was dislodging electrons that were then absorbing energy. Taking advantage of silicon’s electrical properties, they built a tiny component into the silicon that sweeps away the electrons when voltage is applied.
“That was a major remaining milestone for these lasers,” said Bahram Jalali, a University of California, Los Angeles electrical engineering professor who was not involved in the Intel research.
The UCLA team first suggested using the Raman effect for silicon lasers in 2002 and last year reported the first silicon laser. Last week, Jalali and a colleague published a paper in the journal Optics Express that showed the same component used by Intel to sweep away electrons can be used to encode light with data by pumping them in.
But Jalali calls Intel’s laser more significant because it cleared a major technical hurdle and enables practical uses of the technology. And, like his team’s research, it combines both the new optical capabilities and silicon’s well-known electrical characteristics.
“That’s what you need to do if you want to integrate everything on the same chip with electronic circuitry,” Jalali said.
Paniccia sees the lasers — as well as the external silicon optical modulator his lab developed a year ago — as building blocks. The lab also is working on ways to package the devices so that they can be used with existing technology.
“Think of them as Legos,” Paniccia said. “I can mix and match, put them together, depending on the application.”