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Plasmonic bound states in the continuum (BICs) offer a promising route to overcome the intrinsic trade-off between field confinement and radiation loss in nanophotonic systems. By exploiting the coupling of plasmonic and photonic systems, plasmonic BICs can achieve sharp spectral selectivity with strong near-field enhancement, making them attractive for compact and efficient optical devices. However, realizing high-Q resonances in plasmonic structures remains challenging due to Ohmic losses and the requirement of relatively thick metallic films. Here, we numerically demonstrate an ultrathin freestanding photonic–plasmonic membrane that supports hybrid guided and quasi-BIC resonances with record-high Q-factors in plasmonic architectures. By integrating a thin Ag layer (10-20 nm) with a dielectric SiN membrane, the hybrid coupling suppresses radiative leakage while preserving deep-subwavelength confinement, yielding Q-factors exceeding 2370. Remarkably, even when the total thickness of the photonic-plasmonic membrane is reduced to approximately 30 nm, the resonance maintains Q > 1300 with strong near-field intensity, a performance regime that cannot be achieved in metal-only plasmonic systems. The demonstrated strategy resolves the long-standing trade-off between near-field localization and radiative loss in plasmonics by leveraging hybrid BIC formation in an ultrathin membrane platform. Because the architecture is compatible with standard thin-film processing and operates with metal layers only a few tens of nanometers thick, it provides a practical route to compact, high-performance components for nanophotonic sensing, surface-enhanced spectroscopy, quantum emitter coupling, nonlinear optics, and subwavelength optoelectronics.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Plasmonic, Photonic–plasmonic hybrid BICs, Bound states in thecontinuum (BICs), High-Q, Ultrathin metasurface, Nanomembrane

Date published: 2026-12-31

Publisher: Informa UK Limited

Journal:

• Science and Technology of Advanced Materials: Methods (ISSN: 27660400) vol. 6 issue. 1 2639793

Funding:

• JSPS KAKENHI JP23K26155, JP25KF0083

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1080/27660400.2026.2639793

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Updated at: 2026-03-19 14:27:13 +0900

Published on MDR: 2026-03-19 13:36:24 +0900