Breakthrough in Controlling the Transmission of Light

Professor Andrea Alus paper is the cover story of the latest issue of 'Nature Electronics.'

Operation of modern-day technology requires an ever-increasing use of broadband frequency signals. This, in turn, has grown the demand for reliable, efficient methods of signal transmission that prevent interference and are more efficient in their use of the scarcely available frequency spectrum. These requirements are constrained, however, by reciprocity - a law of physics that forces the transmission of light to be identical in opposite directions.

In past decades, scientists and engineers have addressed these challenges with the creation of isolators: devices that use an external magnetic field to force light waves to travel in a single direction. But this form of wave isolation is costly, and it requires the use of large, heavy magnets that demand a lot of device real estate. An additional drawback is that they cannot be integrated into silicon-based circuits and systems.
 
In the cover-story paper published in today's Nature Electronics, researchers at the Advanced Science Research Center (ASRC) at the Graduate Center of the City University of New York (CUNY) and at the University of Texas at Austin detail the development of a new light wave-isolation method that may overcome these challenges. The innovative approach does not require magnets or any other form of "external bias" for reliable wave transmission, yet it ensures highly efficient broad bandwidth isolation.

"We have been working on overcoming reciprocity without magnets for a few years," said Andrea Alu, director of the ASRC's Photonics Initiative and Einstein Professor of Physics at the Graduate Center. "In the past we have explored using devices with moving or time-changing elements, but these approaches pose other technological challenges. In this paper, we show that a non-magnetic device free of an external power source -- thanks to suitably tailored nonlinearities  "can dramatically break transmission symmetry and realize efficient broadband isolation."

Read the full GC news story.