Plasmonics at the Space-Time Limit

The optical response of metallic nanostructures exhibits fascinating properties: Local field interference effects that lead to strong variations of the near field distribution on a subwavelength scale, and long lasting electronic coherences. To circumvent the limitation of optical diffraction we use a photoemission electron microscope (PEEM) that has been proved to be a versatile tool for the investigation of near field properties of nanostructures with nanometer spatial resolution and subfemtosecond time steps [1,2].

The potential of this technique will be demonstrated on two experiments: In a first work, the long-range energy transfer mechanism between two coupled plasmonic whispering gallery nanoantennas in an elliptical cavity has been investigated. We demonstrate periodic coherent energy transfer back and forth over a distance of twice the excitation wavelength [3]. In a second work we experimentally reveal and measure the spatiotemporal dynamics of the formation of plasmonic vortices and their dressing by optical angular momentum. We have manipulated one of the basic properties of light by converting spin angular momentum into orbital angular momentum in a plasmonic Archimedes spiral [4]. By analyzing the time-resolved data in the frequency domain, we show that both single and double angular momentum mixing processes are present, which correspond to different quantum pathways of the electron excitation in 2-photon-photoemission.

[1] M. Aeschlimann et al, Nature 446, 301 (2007)

[2] M. Aeschlimann et al, Science 333, 1723 (2011)

[3] M. Aeschlimann et al, Light: Science & Applications 6, e17111. (2017)

[4] G. Spektor et al, Science 355, 1187 (2017)