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O: Fachverband Oberflächenphysik

O 7: Plasmonics and Nanooptics I

O 7.6: Talk

Monday, March 18, 2024, 11:45–12:00, MA 043

Photon-Induced Near-Field Interaction in Ultrafast Point-Projection Electron Microscopy — •Germann Hergert¹, Andreas Wöste¹, Martin Silies¹, Dong Wang², Petra Groß¹, and Christoph Lienau¹ — ¹Institut für Physik, Carl-von-Ossietzky Universität, 26129 Oldenburg, Germany — ²Institut für Werkstofftechnik, TU Ilmenau, 98693, Germany

Photon-induced electron microscopy (PINEM) utilizes the coherent interaction of swift electrons (10-100keV) with optical near-fields for high-resolution imaging of nano-sized systems. Transferring PINEM to significantly lower electron energies (<100eV) increases the interaction time between electrons and near-fields and may enhance coupling to nano-confined optical modes. However, this interaction has not been demonstrated due to high momentum mismatch at such low energies.

This study presents the first PINEM-like interactions in ultrafast point-projection electron microscopy (UPEM) with 100eV electrons [1]. Plasmonic nanofocusing generates 30fs electron pulses from a sharp gold taper that are accelerated by a -100V bias voltage towards an optically pumped Yagi-Uda antenna milled inside a 13nm thick free-standing gold film. The 3D momentum of the transmitted electrons is detected with a time-of-flight delay-line detector. A spread in the electron's momentum distribution is observed, originating from their coupling to both - longitudinal and transverse - electric field components of the antenna. This paves the way for spatial and temporal characterization of vectorial near fields in UPEM.

[1] Wöste, A. et al., Nano Lett. 23, 5528-5534 (2023)

Keywords: Photon-induced electron microscopy; Ultrafast electron microscopy; Plasmonic near fields; Low-energy electrons; Nanoantenna