Silicon Laser Technology

Professor Bahram Jalali, Director
The Optoelectronics Circuits and Systems Laboratory

Professor Bahram Jalali, whose research team and discoveries have been featured in publications such as Scientific American, Wall Street Journal, the New York Times, Nature, and Science has developed a novel approach to silicon devices that combines light amplification with a photovoltaic effect.

In a paper presented at the 2006 International Optical Amplifiers and Applications Conference in Vancouver, Canada, Prof. Jalali's research group reported that not only can optical amplifi cation in silicon be achieved with zero power consumption, but power can now be generated in the process. The team's research shows that silicon Raman amplifiers possess nonlinear photovoltaic properties, a phenomenon related to power generation in solar cells.

Prior to their work, the Raman effect had not been considered for creating silicon optical devices, since several kilometers of fiber were required to make a useful device, whereas the typical silicon chip is millimeters in size. Through their research, Jalali's group was able to significantly reduce the fiber requirements, realizing the possibility of a silicon laser. "Silicon is a crystal with a wellordered atomic arrangement, compared to glass fiber for example, which is amorphous with a random atomic arrangement," he explains. "This results in a very strong Raman effect in silicon that can be exploited to create a laser on a chip."

Jalali's team determined that the Raman effect - or the changes in wavelength for some light photons caused when passing through transparent material – is 10,000 times stronger in pure silicon than in glass, and can be used to amplify data considerably. The first silicon laser, demonstrated for the first time by Jalali and research engineer Ozdal Boyraz, exhibited nearly ideal characteristics and produced pulsed radiation with a very high peak power of one watt. "We were excited to be the first to demonstrate that a laser can indeed be made on a silicon chip," said Jalali, who is also a member of the California Nano Systems Institute. "Our approach uses the natural atomic vibrations of silicon to create or amplify light, which is significant because no special impurity or complicated device structure is needed."

Professor Jalali, who worked with researcher Sasan Fathpour and graduate student Kevin Tsia in making the recent discovery, says that after dominating the electronics industry for decades, silicon is now on the verge of becoming the material of choice for the photonics industry, the traditional stronghold of today's semiconductors. Silicon photonics technology has the potential to use the power of optical networking inside computers and to create a new generation of miniaturized and low-cost photonic components, among other applications. "This discovery is a step forward and makes it much more likely that photonics and electronics will converge. If they do, many applications that silicon photonics has promised will come to fruition," Jalali said. Jalali's research at UCLA Electrical Engineering was funded by the U.S. Department of Defense through the Defense Advanced Research Project Agency (DARPA) and co-sponsored by the Northrop Grumman Corporation.