Spatial Variations in Femtosecond Field Dynamics within a Plasmonic Nanoresonator Mode.
Nano Lett
; 19(7): 4651-4658, 2019 Jul 10.
Article
en En
| MEDLINE
| ID: mdl-31181160
ABSTRACT
Plasmonic resonators can be designed to support spectrally well-separated discrete modes. The associated characteristic spatial patterns of intense electromagnetic hot-spots can be exploited to enhance light-matter interaction. Here, we study the local field dynamics of individual hot-spots within a nanoslit resonator by detecting characteristic changes of the photoelectron emission signal on a scale of â¼12 nm using time-resolved photoemission electron microscopy (TR-PEEM) and by excitation with the output from a 20 fs, 1 MHz noncollinear optical parametric amplifier (NOPA). Surprisingly, we detect apparent spatial variations of the Q-factor and resonance frequency that are commonly considered to be global properties for a single mode. By using the concept of quasinormal modes we explain these local differences by crosstalk of adjacent resonator modes. Our findings are important in view of time-domain studies of plasmon-mediated strong light-matter coupling at ambient conditions.
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Nano Lett
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2019
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Article