Coherent emission from plasmonic metamaterials

Adamo, G., Ou, J-Y., So, J.-K., Jenkins, S.D., MacDonald, K.F., De Angelis, F., Di Fabrizio, E., Ruostekoski, J. and Zheludev, N.I. (2012) Coherent emission from plasmonic metamaterials. SPIE Photonics Europe 2012, , Brussels, Belgium. 16 - 19 Apr 2012.

Abstract

We report on a fundamentally new radiation phenomenon in nanostructures: emission of spatially coherent and spectrally narrow-band light driven by localized injection of free electrons into a planar plasmonic metamaterial. In 'coherent' metamaterials, where interactions among the meta-molecules are strong, an electron beam can generate a synchronized, in-phase response across a large number of meta-molecules leading to threshold-free emission of spatially coherent light propagating perpendicular to the metamaterial.

In a laser coherence is derived from the bosonic statistics of photons, the resonant properties of the laser cavity and the collective nature of stimulated emission in the gain medium, and a threshold level of input energy is required to maintain the gain and overcome losses. Here we show experimentally that a scalable low-divergence, threshold-free optical source can be constructed on the basis of a collectively oscillating optical nano-antenna array formed by the metamaterial wherein coherence is provided not by the feed (as in conventional microwave antenna arrays) but via the strong mutual interactions among the nano-antennas.

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Contributors

Author: J-Y. Ou

Author: K.F. MacDonald

Author: N.I. Zheludev

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