Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 96: Plasmonics and Nanooptics: Light-Matter Interaction, Spectroscopy II
O 96.4: Vortrag
Freitag, 21. März 2025, 11:15–11:30, H4
Near-field microscopy of complex polaritonic excitations — •Farid Aghashirinov1, Bettina Frank1, Harald Giessen1, Andrea Manchini2, Lin Nan2, Giacomo Venturi2, Nicola Melchioni2, and Antonio Ambrosio2 — 14-th Physics Institute, University of Stuttgart, Stuttgart, Germany — 2Vectorial Nano-Imaging, Istituto Italiano di Tecnologia, Milano, Italy
We investigate directional near-infrared (NIR) plasmon polaritons (PPs) in mechanically exfoliated bulk molybdenum oxide dichloride (MoOCl2) flakes on a glass substrate with gold disk launchers positioned on top of the flakes, through experimental and theoretical methods [1]. MoOCl2, a natural van der Waals crystal, exhibits low-loss, in-plane hyperbolic PPs across the visible and NIR ranges, and displays a unique anisotropic optical response based on the polarization of the incident light. When light polarization aligns with the flake’s shortest axis, MoOCl2 behaves optically metallic, while aligning with the longest axis reveals a dielectric behaviour. To experimentally study the hyperbolic PPs in MoOCl2, we use a near-field excitation and detection approach. Gold disks serve as excitation sources, scattering incident light to couple it with the material’s polaritonic modes, while a reflection scattering-type scanning near-field optical microscope (s-SNOM) enables subwavelength imaging. For tunable wavelength illumination, we use a broadband laser from Stuttgart Instruments (SI), which, when combined with s-SNOM, allows us to investigate these modes across a wide wavelength range, capturing detailed insights into their behavior and propagation. [1] G. Venturi et al., Nat Commun 15, 9727 (2024)
Keywords: Plasmon polaritons; Molybdenum oxide dichloride (MoOCl2); Scattering SNOM; Near - field optics; Tunable broadband laser