Breakthrough İn Photonic Chip Research Paves Way For Ultrafast İnformation Sharing

Researchers at the California Institute of Technology and the University of California, San Diego have discovered a way to prevent light signals on a silicon chip from reflecting backwards and interfering with its operation. Otherwise, the light beams would interfere with lasers and other photonic components on the chip and make the chip unstable. The breakthrough marks a significant achievement in the development of integrated photonic chips that could replace electronic chips as the backbone of information technology. Their findings are published Aug. 5 in the journal Science. Although information systems now rely primarily on fiber optic networks to connect and share data around the world using photons instead of electrons, the underlying computer technology is still based on electronic chips, which are slower and more prone to data loss than photonic chips. Lab versions of photonic chips being developed across the industry are already supporting data transfer rates of 10 gigabits per second, and in just five years, photonic chips could achieve data transfer rates of over 40 Gbps – an order of magnitude higher than the speed of today's networks. The shift towards optical networks will make information sharing faster, more energy-efficient and less costly.

Electronic chips rely on a diode to isolate electrical signals, enabling current to travel in just one direction and prevent interference. Lead researcher Liang Feng, a postdoctoral fellow at Caltech who earned his doctorate in electrical engineering from the UC San Diego Jacobs School of Engineering in 2010, said engineers have been trying to duplicate the diode system on photonic chips for 20 years.

The Caltech-UC San Diego research team developed a metallic-silicon optical waveguide system to channel light so it travels in different patterns depending on its propagation direction. The pattern is symmetric when traveling forward and asymmetric when reflected backwards along the same path. Similar to the diode in electronics, the backscattered light is dissipated as a result.

"This discovery will help to realize a long-term goal of combining electronics with photonics to enable scalable, energy-efficient and cost-effective technology that will have a tremendous impact on such information systems as supercomputers, the Internet, and data centers," said Yeshaiahu (Shaya) Fainman, professor and chair of the UC San Diego Department of Electrical and Computer Engineering. "Computer technology will be able to handle a lot more data, faster and at lower cost, which will benefit large-scale business and government users as well as gadget-loving consumers."

It was during graduate work under the direction of Fainman in 2006, that Feng said he began thinking about how to achieve this kind of "nonreciprocal light propagation" while trying to develop optical metamaterials to manipulate the way light travels.

"Although that particular project was not successful, I never gave up trying to make it work," said Feng.

He credits the multidisciplinary training he received under Fainman at UCSD – including optics, electromagnetics and physics – for building his knowledge in design, fabrication and measurement that made his discovery possible. So it was inevitable that Feng turned to his former professor, Fainman, and UCSD graduate student Maurice Ayache to conduct the measurement and analysis for the experiment that ultimately proved Feng's idea works.