Prof’s research proves possibility of silicon lasers

Saturday, January 20, 2007

Silicon can be altered to emit light, according to a paper by Professor of Engineering Jingming Xu and his research team that will be published in the journal “Nature Materials” today.

Xu’s discovery disproves the conventional wisdom that silicon cannot be used in lasers, a development that may have major implications for computer technology.

Xu, who came to Brown from the Univer-sity of Toronto six years ago, is currently the principal investigator at the University’s Laboratories for Emerging Technologies, which studies nano-materials – particles less than one-billionth of a meter in size.

Current theory suggests that the creation of a silicon laser will lead to the integration of optics and electronics, according to a recent article in “Scientific American.” Lasers have become indispensable for many tasks, from burning CDs to aiming smart bombs, and also lay the groundwork for high-speed communication along fiberoptic cables, which are far superior to copper wires.

Xu’s laser could be applied to light-speed communication abilities within computers, which experts argue would make current laptops remnants of the past.

The major obstacle in the creation of a silicon laser is that silicon does not emit light in its natural state, making it a poor candidate for use in lasers.

However, defying conventional wisdom has been an integral part of Xu’s philosophy, inspiring him to prove it was, in fact, possible to make silicon emit light.

“I’ve always been in the business of trying to do the impossible thing that has never been done before,” Xu said.

The undertaking was initially categorized as a “high-risk, high-reward” project by Xu’s team because their idea had a high chance of failure.

According to Sylvain Cloutier GS, whom Xu described as “a leading force in the group,” the lab’s central goal was to make nano-level changes to the silicon atoms that would increase their suitability for use in lasers, something Cloutier called “nano-photonics.”

Xu and Cloutier recalled that the first six months were spent seeing if “something real was there.” Once they established that their project might be feasible, the remainder of the time was spent “optimizing and working with the materials involved.” In all, the project lasted one-and-a-half years.

Research team meetings were held in room 423A of Barus and Holley, or as Xu’s students and co-workers call it, the “Opportunity Room.”

As the project neared completion, Cloutier told The Herald that silicon optics could make a computer approximately 135,000 times faster than computers using current electrical technology.

“People would dream of having a computer with silicon-based optics,” Cloutier said.

Xu was hesitant to immediately embrace the applications of the laser without further testing and development. He related the pace of his work with lasers to that of the Wright brothers with airplanes.

“First you prove you can do it,” Xu said. “Then you try to do it larger, longer, higher and under non-ideal conditions.” Only after that, he said, should researchers look into potential uses of a new technology.

Cloutier and Xu said that those who argued that the creation of a silicon laser was impossible due to the element’s physical properties overlooked the fact that the material would not have to be in its original form.

Xu, who currently teaches EN 263: “Electro-Optical Properties of Materials and Biomolecules,” said he hopes the publication of his work in “Nature Materials” will attract other scientists to his ideas.

Last month Xu was one of the two Brown faculty members to receive the esteemed Guggenheim Fellowship Award. Given by the John Simon Guggenheim Memorial Foundation, the award is meant to honor researchers of all fields for their academic success and ingenuity.

Winners of the fellowship were singled out from over 3,000 applicants and were commended for their “distinguished achievement in the past and exceptional promise for future accomplishment,” according to the foundation’s Web site.

Reflecting on his career, Xu described himself as possessing an “artist’s impulse” when it came to his work with science.

Xu said creativity and originality were integral to succeed in his line of work, since he and his team are the ones clearing a new path for the scientists to come.

Aside from the most recent article in “Nature Materials,” Xu and his team are responsible for 159 other publications, as well as a textbook chapter on carbon nanotube engineering and physics. The lab has also received several major patents and created multiple software developments.