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Nano Lett. 2014 Nov 12;14(11):6651-4. doi: 10.1021/nl503324g. Epub 2014 Oct 20.

Probing the quantum tunneling limit of plasmonic enhancement by third harmonic generation.

Author information

1
Department of Electrical and Computer Engineering, University of Victoria , Victoria, British Columbia V8P5C2, Canada.

Abstract

Metal nanostructures provide extreme focusing of optical energy that is limited fundamentally by quantum tunneling. We directly probe the onset of the quantum tunneling regime observed by a sharp reduction in the local field intensity in subnanometer self-assembled monolayer gaps using third harmonic generation. Unlike past works that have inferred local limits from far-field spectra, this nonlinear measurement is sensitive to the near-field intensity as the third power. We calculate the local field intensity using a quantum corrected model and find good quantitative agreement with the measured third harmonic. The onset of the quantum regime occurs for double the gap size of past studies because of the reduced barrier height of the self-assembled monolayer, which will be critical for many applications of plasmonics, including nonlinear optics and surface enhanced Raman spectroscopy.

KEYWORDS:

local near-field; quantum corrected model; quantum tunneling; third harmonic generation

PMID:
25322471
DOI:
10.1021/nl503324g

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