Regensburg 2025 – scientific programme
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O: Fachverband Oberflächenphysik
O 87: Plasmonics and Nanooptics: Light-Matter Interaction, Spectroscopy I
O 87.10: Talk
Thursday, March 20, 2025, 17:15–17:30, H4
How accurate is the pole expansion of the scattering matrix? — •Elias Fösleitner1, Adrià Canós Valero1, Egor Muljarov2, and Thomas Weiss1 — 1Department of Theoretical Physics, University of Graz, Graz, Austria — 2School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom
Optical metasurfaces are flat arrangements of nanostructures with different subwavelength sizes and orientations, which allow tailoring the light propagation in a layer of subwavelength thickness. Such metasurfaces are often described using their resonant states. These states, also known as quasi-normal modes, serve as the foundation for the pole expansion of the optical scattering matrix, providing a more efficient and insightful alternative to conventional full-wave simulations. Existing formulations of such an expansion have, however, limitations, particularly in terms of accuracy, efficiency, and convergence. The aim of this study is to compare different approaches for pole expansions and identify their advantages and limitations. Moreover, we discuss how the choice of basis functions of the scattering matrix influences its complex pole structure and the resulting pole expansion. Overall, these findings will allow for a faster prediction of optical properties by choosing the best suited resonant expansion and also provide additional insight that is necessary for many applications such as nanophotonic sensors.
Keywords: Nanooptics; Plasmonics; Metasurfaces; Pole Expansion; Scattering matrix