Mapping the electromagnetic field confinement in the gap of germanium nanoantennas with plasma wavelength of 4.5 micrometers

Eugenio Calandrini, Tommaso Venanzi, Felice Appugliese, Michela Badioli, Valeria Giliberti, Leonetta Baldassarre, Paolo Biagioni, Francesco De Angelis, Wolfgang M. Klesse, Giordano Scappucci, Michele Ortolani

Research output: Contribution to journalArticleScientificpeer-review

13 Citations (Scopus)
32 Downloads (Pure)

Abstract

We study plasmonic nanoantennas for molecular sensing in the mid-infrared made of heavily doped germanium, epitaxially grown with a bottom-up doping process and featuring free carrier density in excess of 1020 cm-3. The dielectric function of the 250 nm thick germanium film is determined, and bow-tie antennas are designed, fabricated, and embedded in a polymer. By using a near-field photoexpansion mapping technique at λ = 5.8 μm, we demonstrate the existence in the antenna gap of an electromagnetic energy density hotspot of diameter below 100 nm and confinement volume 105 times smaller than λ3.

Original languageEnglish
Article number121104
JournalApplied Physics Letters
Volume109
Issue number12
DOIs
Publication statusPublished - 19 Sep 2016

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