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

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

Calandrini, Eugenio (Istituto Italiano di Tecnologia)
Venanzi, Tommaso (Sapienza University of Rome)
Appugliese, Felice (Sapienza University of Rome)
Badioli, Michela (Sapienza University of Rome)
Giliberti, Valeria (Sapienza University of Rome; Istituto Italiano di Tecnologia)
Baldassarre, Leonetta (Sapienza University of Rome; Istituto Italiano di Tecnologia)
Biagioni, Paolo (Politecnico di Milano)
De Angelis, Francesco (Istituto Italiano di Tecnologia)
Klesse, Wolfgang M. (University of New South Wales)
Scappucci, G. (TU Delft QCD/Scappucci Lab; University of New South Wales)
Ortolani, Michele (Sapienza University of Rome)

2016-09-19

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.

http://resolver.tudelft.nl/uuid:96f50a44-5005-47e9-a782-e1d48e766fc4

https://doi.org/10.1063/1.4962976

2017-09-01

0003-6951

Applied Physics Letters, 109 (12)

Institutional Repository

journal article

© 2016 Eugenio Calandrini, Tommaso Venanzi, Felice Appugliese, Michela Badioli, Valeria Giliberti, Leonetta Baldassarre, Paolo Biagioni, Francesco De Angelis, Wolfgang M. Klesse, G. Scappucci, Michele Ortolani