Article // Increased rise time of electron temperature during adiabatic plasmon focusing

Decay of plasmons to hot carriers has recently attracted considerable interest for funda- mental studies and applications in quantum plasmonics. Although plasmon-assisted hot carriers in metals have already enabled remarkable physical and chemical phenomena, much remains to be understood to engineer devices. Here, we present an analysis of the spatio- temporal dynamics of hot electrons in an emblematic plasmonic device, the adiabatic nanofocusing surface-plasmon taper. With femtosecond-resolution measurements, we con- firm the extraordinary capability of plasmonic tapers to generate hot carriers by slowing down plasmons at the taper apex. The measurements also evidence a substantial increase of the “lifetime” of the electron gas temperature at the apex. This interesting effect is inter- preted as resulting from an intricate heat flow at the apex. The ability to harness the “lifetime” of hot-carrier gases with nanoscale circuits may provide a multitude of applications, such as hot-spot management, nonequilibrium hot-carrier generation, sensing, and photovoltaics.

Olga Lozan 1, Ravishankar Sundararaman 2, Buntha Ea-Kim 3, Jean-Michel Rampnoux 1, Prineha Narang 4, Stefan Dilhaire 1 & Philippe Lalanne 5

DOI: 10.1038/s41467-017-01802-y

1 Laboratoire Onde et Matière d’Aquitaine (LOMA), UMR 5798, CNRS-Université de Bordeaux, 33400 Talence, France. 2 Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA. 3 Laboratoire Charles Fabry (LCF), UMR 5298, CNRS-IOGS-Université Paris XI, Institut d’Optique, 91120 Palaiseau, France. 4 Faculty of Arts and Sciences, Harvard University, Cambridge, MA 02138, USA. 5 Laboratoire Photonique, Numérique et Nanosciences (LP2N), UMR 5298, CNRS-IOGS-Université de Bordeaux, Institut d’Optique d’Aquitaine, 33400 Talence, France. Correspondence and requests for materials should be addressed to S.D. (email: stefan.dilhaire@u-bordeaux.fr) or to P.L. (email: Philippe.Lalanne@institutoptique.fr)