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Journal of Photonics for Energy

Hot-electron-induced light amplification
Author(s): Kai Braun; Xiao Wang; Dai Zhang; Alfred J. Meixner
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Paper Abstract

Electromagnetic coupling between resonant plasmonic oscillations of two closely spaced noble metal particles can lead to a strongly enhanced optical near field in the cavity formed by the gap between the metal particles. However, discoveries in quantum plasmonics show that an upper limit is imposed to the field enhancement by the intrinsic nonlocality of the dielectric response of the metal and the tunneling of the coherently oscillating conduction electrons through the gap. Here, we introduce and experimentally demonstrate optical amplification by radiative relaxation of hot electrons in a tunneling junction of a scanning tunneling microscope forming an extremely small point light source. When electrons tunnel from the sample to the tip, holes are left behind. These can be repopulated by hot electrons induced by the laser-driven plasmon oscillation on the metal surfaces enclosing the cavity and lead to a much higher electron to photon conversion efficiency. The dynamics of this system can be described by rate equations similar to laser equations. They show that the repopulation process can be efficiently stimulated by the gap mode’s near field. Our results demonstrate how optical enhancement inside the plasmonic cavity can be further increased by a stronger localization via tunneling through molecules.

Paper Details

Date Published: 18 August 2016
PDF: 11 pages
J. Photon. Energy 6(4) 042506 doi: 10.1117/1.JPE.6.042506
Published in: Journal of Photonics for Energy Volume 6, Issue 4
Show Author Affiliations
Kai Braun, Eberhard Karls Univ. Tübingen (Germany)
Xiao Wang, Eberhard Karls Univ. Tübingen (Germany)
Dai Zhang, Eberhard Karls Univ. Tübingen (Germany)
Alfred J. Meixner, Eberhard Karls Univ. Tübingen (Germany)


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