Plasmonic mid-infrared third harmonic generation in germanium nanoantennas

Fischer, M. P. et al. (2018) Plasmonic mid-infrared third harmonic generation in germanium nanoantennas. Light: Science and Applications, 7(1), 106. (doi: 10.1038/s41377-018-0108-8) (PMID:30564312) (PMCID:PMC6290006)

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We demonstrate third harmonic generation in plasmonic antennas consisting of highly doped germanium grown on silicon substrates and designed to be resonant in the mid-infrared frequency range that is inaccessible with conventional nonlinear plasmonic materials. Owing to the near-field enhancement, the result is an ultrafast, subdiffraction, coherent light source with a wavelength tunable between 3 and 5 µm, and ideally overlapping with the fingerprint region of molecular vibrations. To observe the nonlinearity in this challenging spectral window, a high-power femtosecond laser system equipped with parametric frequency conversion in combination with an all-reflective confocal microscope setup is employed. We demonstrate spatially resolved maps of the linear scattering cross section and the nonlinear emission of single isolated antenna structures. A clear third-order power dependence as well as mid-infrared emission spectra prove the nonlinear nature of the light emission. Simulations support the observed resonance length of the double-rod antenna and demonstrate that the field enhancement inside the antenna material is responsible for the nonlinear frequency mixing.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Paul, Professor Douglas and Gallacher, Dr Kevin
Authors: Fischer, M. P., Riede, A., Gallacher, K., Frigerio, J., Pellegrini, G., Ortolani, M., Paul, D. J., Isella, G., Leitenstorfer, A., Biagioni, P., and Brida, D.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:Light: Science and Applications
Publisher:Nature Publishing Group
ISSN (Online):2047-7538
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in Light: Science and Applications 7(1):106
Publisher Policy:Reproduced under a Creative Commons License
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
694301Engineering Quantum Technology Systems on a Silicon PlatformDouglas PaulEngineering and Physical Sciences Research Council (EPSRC)EP/N003225/1ENG - ENGINEERING ELECTRONICS & NANO ENG