Dresden 2026 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 79: Plasmonics and nanooptics: Light-matter interaction, spectroscopy III

O 79.2: Vortrag

Donnerstag, 12. März 2026, 10:45–11:00, HSZ/0403

Compressing few-cycle optical near fields in the tip-sample junction of a scanning probe microscope — •Sam S. Nochowitz, Tom Jehle, Juanmei Duan, and Christoph Lienau — Institute of Physics, University of Oldenburg, 26129 Germany

Plasmonic nanogaps confine light to dimensions in the nanometer or even sub-nanometer range while simultaneously enhancing the local electromagnetic field strength. This spatial confinement of light led to dramatic advances in nanosensing (1) and tip-enhanced Raman Spectroscopy. So far, the time dynamics of the fields emitted from such nanocavities have achieved little attention. Here, we introduce a broadband interferometric scattering-type SNOM technique to reconstruct amplitude and phase of light scattered from a sharp gold taper acting as a near-field probe. We isolate the near-field that is scattered from the apex and quantitatively measure its time structure (2). The apex field decays within 6 fs, a decay time mainly given by the radiative damping of the apex mode. Upon approaching the tip to a gold surface, the coupling of the apex field to its image dipole results in 2-fold reduction in the decay time to less than 2.7 fs, caused by phase shifts in the apex response, predicted in FDTD simulations (3). Our results pave the way towards linear and nonlinear ultrafast oscilloscopy with nm/fs resolution. (1) R. J. Chikkardy et al., Nature 535, 127 (2016); (2) T. Jehle, submitted (2025). (3) S. Thomas et al. New J. Phys. 17 (2015).

Keywords: Ultrafast nanoscopy; Ultrafast optical near fields; sSNOM; spectral interferometry; Ultrafast oscilloscopy