https://doi.org/10.1140/epjd/s10053-026-01127-w
Research - Photons
Multi-mode optical absorber and sensor based on quasi-bound states in the continuum formed in double-layer metasurface
School of Physics and Electronic Science, Changsha University of Science and Technology, Street, 410004, Changsha, China
a
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Received:
21
September
2025
Accepted:
1
February
2026
Published online:
22
February
2026
Abstract
Quasi-bound state in the continuum (quasi-BIC) is driving research direction in optical absorbing and sensing owing to the extremely narrow linewidth with almost non-radiative loss. However, it is usually revealed with a certain polarized light due to the asymmetry requirement and mainly holds for single or dual modes, making it unsuitable for many practical applications. Here we propose the multi-mode optical absorber and sensor that utilizes quasi-BIC based on periodically arranged double-layer silicon elliptical ring metasurface. By introducing asymmetry perturbation through separating the centers of the elliptic ring, the symmetry-protected BIC converts into leaky resonances, leading to the emergence of two Fano resonances and an electromagnetically induced transparency (EIT) for the x-polarized incident light, and three Fano resonances and an EIT for the y-polarized incident light. The multipole decomposition analysis and temporal coupled mode theory are employed to explain the underlying physics. Subsequently, this BIC-inspired metasurfaces is demonstrated as refractive index sensor with the maximal sensitivity 
nm/RIU and is utilized to enhance the optical absorption of graphene with the theoretical maximum absorption. Our results offer a possible solution for multi-mode quasi-BICs and open up possibilities for optical modulation and optical device development.
submitted to:The European Physical Journal D.
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1140/epjd/s10053-026-01127-w.
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© The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature 2026
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
