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Spatially encoded polaritonic ultra-strong coupling in gradient metasurfaces with epsilon-near-zero modes
Publikationstyp
Journal Article
Date Issued
2025-09-12
Sprache
English
Author(s)
Baù, Enrico
Aigner, Andreas
Biechteler, Jonas
Heimig, Connor
Gölz, Thorsten
Journal
Volume
38
Issue
1
Article Number
e10402
Citation
Advanced Materials 38 (1): e10402 (2025)
Publisher DOI
Scopus ID
A platform is introduced to achieve ultra-strong coupling (USC) between light and matter using widely available materials. USC is a light–matter interaction regime characterized by coupling strengths exceeding 10% of the ground state energy. It gives rise to novel physical phenomena, such as efficient single-photon coupling and quantum gates, with applications in quantum sensing, nonlinear optics, and low-threshold lasing. Although early demonstrations in plasmonic systems have been realized, achieving USC in dielectric platforms, which offer lower losses and high Q-factors, remains challenging due to typically low mode overlap between the photonic field and the material resonance. Here, dielectric dual gradient metasurfaces supporting quasi-bound-states-in-the-continuum are leveraged to spatially encode both the spectral and coupling parameter space and demonstrate USC to an epsilon-near-zero (ENZ) mode in an ultra-thin SiO₂ layer. The strong out-of-plane electric fields in tapered bar structure overlap exceptionally well with those of the ENZ mode, resulting in a normalized coupling strength of η = 0.10 and a mode splitting equivalent to 20% of the ENZ mode energy; a four-to-five-fold increase compared to previous approaches. The strong field confinement of the approach opens new possibilities for compact and scalable polaritonic devices, such as tunable frequency converters and low-energy optical modulators.
Subjects
bound-states-in-the-continuum
epsilon-near-zero
light–matter interaction
polaritonics
ultra-strong coupling
DDC Class
600: Technology