November 12, 2010
Controlling the flow of light with a novel optical transistor
Controlling and modulating the flow of light is essential in today's telecommunications-based society. Professor Tobias Kippenberg and his team in EPFL's Laboratory of Photonics and Quantum Measurements have discovered a novel way to couple light and vibrations. Using this discovery, they built a device in which a beam of light traveling through an optical microresonator could be controlled by a second, stronger light beam. The device thus acts like an optical transistor, in which one light beam influences the intensity of another.
"We have known for more than two years that this effect was theoretically possible," explains Max-Planck Institute scientist Albert Schliesser, but pinning it down proved difficult. "Once we knew where to look, it was right there," recalls EPFL PhD student Stefan Weis, one of the lead authors of the paper. Senior EPFL scientist Samuel Del©glise notes that "the agreement between theory and experiment is really striking."
Applications of this novel effect, baptised "OMIT" (optomechanically-induced transparency), could provide entirely new functionality to photonics. Radiation-to-vibration conversions are already widely used; in mobile phones, for example, a receiver converts electromagnetic radiation to mechanical vibration, enabling the signal to be filtered efficiently. But it has been impossible to do this kind of conversion with light. With an OMIT-based device, an optical light field could for the first time be converted into a mechanical vibration. This could open up a huge range of possibilities in telecommunications. For example, novel optical buffers could be designed that could store optical information for up to several seconds.
On a more fundamental level, researchers around the world have been trying to find ways to control optomechanical systems at the quantum level: the switchable coupling demonstrated by the EPFL-Max Planck team could help the community clear this hurdle, by serving as an important interface in hybrid quantum systems.
On the Net: