Cambridge, Mass., December 6, 2010 Utilizing a century-old phenomenon discovered in St. Paul's Cathedral, London, applied scientists at Harvard University have demonstrated, for the first time, highly collimated unidirectional microlasers.
The result of a collaboration with researchers from Hamamatsu Photonics in Hamamatsu City, Japan, and the Institute of Theoretical Physics of the University of Magdeburg, Germany, the advance has a wide range of new applications in photonics such as sensing and communications.
Published online this week in the Proceedings of the National Academy of Sciences, the research team took advantage of a concept in physics referred to as "whispering gallery modes."
Over a century ago, British scientist Lord Rayleigh wondered how two people standing on opposite sides of the dome in St. Paul's Cathedral could hear each other by whispering into the circular wall. He discovered that the sound skirts along the smooth surface of the wall with negligible attenuation due to scattering or absorption.
The optical analog of whispers in a dome are light rays confined to the perimeter of tiny circular disks by multiple reflections from the boundary as they circle around. Because attenuation is minimal within the smooth disk, these resonators have already been used to make some of the world's lowest-threshold lasers. Circular disks, however, have posed certain challenges.
"One of the crucial unsolved problems of these microlasers for practical applications has been that their emission is non-directional and their optical power output is negligible," said team leader Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at Harvard's School of Engineering and Applied Sciences (SEAS).
"Light gets trapped by these whispering gallery modes with little chance to escape except by a faint isotropic emission. Strateg
|Contact: Caroline Perry|