Plasmonic whispering gallery microcavity paves the way to future ...( The principle behind whispering gall...)

The principle behind whispering galleries where words spoken softly beneath a domed ceiling or in a vault can be clearly heard on the opposite side of the chamber has been used to achieve what could prove to be a significant breakthrough in the miniaturization of lasers. Ultrasmall lasers, i.e., nanoscale, promise a wide variety of intriguing applications, including superfast communications and data handling (photonics), and optical microchips for instant and detailed chemical analyses.

Researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the California Institute of Technology have developed a "whispering gallery microcavity" based on plasmons - electromagnetic waves that race across the surfaces of metals. Such a plasmon wave has very small wavelength compared with the light, enabling the scaling down optical devices beyond diffraction limit of the light. Cavities are the confined spaces in lasers where light amplification takes place and this new micro-sized metallic cavity for plasmons improves on the quality of current plasmonic cavities by better than an order of magnitude.

"We have shown for the first time that metallic microcavities based on surface plasmons can have a large quality factor and can thereby enable ultra-small device fabrication and strong enhancement of the light," said Xiang Zhang, a mechanical engineer who holds a joint appointment with Berkeley Lab's Materials Sciences Division and the University of California (UC) Berkeley where he directs the NSF Nano-scale Science and Engineering Center.

"Plasmonic microcavities have uniquely different physical properties when compared to dielectric cavities and can extend microcavity research in entirely new ways, particularly at nanoscale dimensions," said Kerry Vahala, a physics professor at Cal Tech and authority on photonic devices. "Our work shows that the full potential of this new class of device can be realiz
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