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Near-field spectroscopy and tuning of subsurface modes in plasmonic terahertz resonators

Mitrofanov, O; Todorov, Y; Gacemi, D; Mottaghizadeh, A; Sirtori, C; Brener, I; Reno, JL; (2018) Near-field spectroscopy and tuning of subsurface modes in plasmonic terahertz resonators. Optics Express , 26 (6) pp. 7437-7450. 10.1364/OE.26.007437. Green open access

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Abstract

Highly confined modes in THz plasmonic resonators comprising two metallic elements can enhance light-matter interaction for efficient THz optoelectronic devices. We demonstrate that sub-surface modes in such double-metal resonators can be revealed with an aperture-type near-field probe and THz time-domain spectroscopy despite strong mode confinement in the dielectric spacer. The sub-surface modes couple a fraction of their energy to the resonator surface via surface waves, which we detected with the near-field probe. We investigated two resonator geometries: a λ/2 double-metal patch antenna with a 2 μm thick dielectric spacer, and a three-dimensional meta-atom resonator. THz time-domain spectroscopy analysis of the fields at the resonator surface displays spectral signatures of sub-surface modes. Investigations of strong light-matter coupling in resonators with sub-surface modes therefore can be assisted by the aperture-type THz near-field probes. Furthermore, near-field interaction of the probe with the resonator enables tuning of the resonance frequency for the spacer mode in the antenna geometry from 1.6 to 1.9 THz (~15%).

Type: Article
Title: Near-field spectroscopy and tuning of subsurface modes in plasmonic terahertz resonators
Open access status: An open access version is available from UCL Discovery
DOI: 10.1364/OE.26.007437
Publisher version: http://doi.org/10.1364/OE.26.007437
Language: English
Additional information: Copyright Optics Express © 2018. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10046451
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