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Revealing mode formation in quasi-bound states in the continuum metasurfaces via near-field optical microscopy
Publikationstyp
Journal Article
Date Issued
2024-08-02
Sprache
English
Author(s)
Gölz, Thorsten
Baù, Enrico
Aigner, Andreas
Barkey, Martin
Keilmann, Fritz
Journal
Volume
36
Issue
38
Article Number
2405978
Citation
Advanced Materials 36 (38): 2405978 (2024)
Publisher DOI
Scopus ID
Publisher
Wiley-VCH
Photonic metasurfaces offer exceptional control over light at the nanoscale, facilitating applications spanning from biosensing, and nonlinear optics to photocatalysis. Many metasurfaces, especially resonant ones, rely on periodicity for the collective mode to form, which makes them subject to the influences of finite size effects, defects, and edge effects, which have considerable negative impact at the application level. These aspects are especially important for quasi-bound state in the continuum (BIC) metasurfaces, for which the collective mode is highly sensitive to perturbations due to high-quality factors and strong near-field enhancement. Here, the mode formation in quasi-BIC metasurfaces on the individual resonator level using scattering scanning near-field optical microscopy (s-SNOM) in combination with a new image processing technique, is quantitatively investigated. It is found that the quasi-BIC mode is formed at a minimum size of 10 × 10-unit cells much smaller than expected from far-field measurements. Furthermore, it is shown that the coupling direction of the resonators, defects and edge states have pronounced influence on the quasi-BIC mode. This study serves as a link between the far-field and near-field responses of metasurfaces, offering crucial insights for optimizing spatial footprint and active area, holding promise for augmenting applications such as catalysis and biospectroscopy.
Subjects
bound states in the continuum
mid-infrared
near-field microscopy
optical metasurfaces
SNOM
DDC Class
600: Technology