Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 96: Plasmonics and Nanooptics: Light-Matter Interaction, Spectroscopy II

O 96.2: Talk

Friday, March 21, 2025, 10:45–11:00, H4

Squeezing few-cycle light pulses in space and time in the gap of a nanoplasmonic resonator — •Tom Jehle, Sam S. Nochowitz, Juanmei Duan, and Christoph Lienau — Universität Oldenburg, D-26129, Germany

The spatial confinement of light to (sub-)nanometer spot sizes in the gap of a nanoparticle-on-mirror resonator or in the gap of a tunnelling junction has led to dramatic advances in nanosensing [1] and tip-enhanced Raman Spectroscopy [2]. So far, the time dynamics of the fields emitted from such nanocavities have achieved little attention and only recently the time structure of a Terahertz field scattered from the junction of an STM tip could be recorded [3]. Here, we introduce a broadband interferometric scattering-type SNOM technique [4] to reconstruct amplitude and phase of light scattered from a sharp gold taper acting as a near-field probe. Direct Fourier transform gives the time structure of the electric field. We distinguish the near-field scattered from the apex and that emitted by spatially well separated scattering mode of the taper. The apex field decays within 13 fs, a decay time mainly given by the radiative damping of the apex mode. Upon approaching the tip to a gold surface, we observe a 3.5-fold reduction in the decay time to less than 4 fs: coupling to the image dipole drastically increases the radiative damping in the tip-surface junction. 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] R. Zhang et al., Nature 531, 623 (2016); [3] T. Siday et al., Nature 629 (2024); [4] J. Zhan et al., Nano Lett. 2024

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