Abstract
Metallic nanostructures support extreme localization and enhancement of optical fields via surface-plasmon (SP) resonances. Although SP are associated with giant enhancements of nonlinear phenomena such as second-harmonic generation (SHG), the role of SP in the process, whether as a field-enhancing catalyst or as a quasiparticle converted in the interaction, has remained experimentally elusive. We demonstrate how -space spectroscopy can distinguish between the plasmonic and photonic SHG processes that occur in a metal nanofilm when it is optically driven via the Kretschmann geometry. The results revealed a nonlinear interaction where two SP annihilate to create a second-harmonic photon. This knowledge has implications for realizing the inverse process, plasmonic parametric down-conversion, which could act as a coherent source of entangled SP pairs.
- Received 20 December 2011
DOI:https://doi.org/10.1103/PhysRevLett.108.136802
© 2012 American Physical Society
Viewpoint
Mirror, Mirror
Published 26 March 2012
Collective electron excitations in metals, called plasmons, can play an important role in second-harmonic generation of light.
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