Normal-Incidence PEEM Imaging of Propagating Modes in a Plasmonic Nanocircuit.

Razinskas, Gary; Kilbane, Deirdre; Melchior, Pascal; Geisler, Peter; Krauss, Enno; Mathias, Stefan; Hecht, Bert; Aeschlimann, Martin · Nano Lett · 2016

basic_science · Level V

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Abstract

The design of noble-metal plasmonic devices and nanocircuitry requires a fundamental understanding and control of the interference of plasmonic modes. Here we report the first visualization of the propagation and interference of guided modes in a showcase plasmonic nanocircuit using normal-incidence nonlinear two-photon photoemission electron microscopy (PEEM). We demonstrate that in contrast to the commonly used grazing-incidence illumination scheme, normal-incidence PEEM provides a direct image of the structure's near-field intensity distribution due to the absence of beating patterns and despite the transverse character of the plasmonic modes. Based on a simple heuristic numerical model for the photoemission yield, we are able to model all experimental findings if global plane wave illumination and coupling to multiple input/output ports, and the resulting interference effects are accounted for.