Refractive index sensing by all-dielectric metasurfaces supporting quasi-bound states in the continuum

Mohsen Samadi; Fatemeh Abshari; J. F. Algorri; P. Roldán-Varona; L. Rodríguez-Cobo; J. M. López-Higuera; J. M. Sánchez-Pena; D. C. Zografopoulos; F. Dell'Olio

doi:10.1117/12.2608256

4 March 2022 Refractive index sensing by all-dielectric metasurfaces supporting quasi-bound states in the continuum

Mohsen Samadi, Fatemeh Abshari, J. F. Algorri, P. Roldán-Varona, L. Rodríguez-Cobo, J. M. López-Higuera, J. M. Sánchez-Pena, D. C. Zografopoulos, F. Dell'Olio

Author Affiliations +

Proceedings Volume 11987, Laser Resonators, Microresonators, and Beam Control XXIV; 119870B (2022) https://doi.org/10.1117/12.2608256
Event: SPIE LASE, 2022, San Francisco, California, United States

Abstract

All-dielectric metasurfaces have attracted increasing attention due to their negligible losses and sharper resonances compared to their metallic counterparts. In this work, we numerically studied the optical performance of a novel alldielectric metasurface based on complementary split-ring resonators (CSRRs), in which ultrathin slots were periodically etched in a thin silicon layer. The proposed CSRR metasurface exhibits two multipolar resonances in the near-infrared (NIR) window. Moreover, a quasi-bound state in the continuum (quasi-BIC) with an ultra-high quality factor can be excited by breaking the symmetry of the structure. Taking advantage of the high-quality factor quasi-BIC mode and its sensitivity to the superstrate medium refractive index (S = Δλ_res/Δn), we design an ultra-high figure of merit (FoM = S/FWHM) refractive index sensor for biomedical applications. By three-dimensional finite element method (3D-FEM), we evaluate the sensitivity of the sensing device to the variation of the superstrate refractive index in the range 1.31-1.33, which is typical for aqueous solutions. Our simulations reveal that a sensitivity of S ~ 155 nm RIU^-1 and an extraordinary FoM ~ 387500 RIU^-1 can be achieved using the ultra-narrow quasi-BIC resonance in the CSRR metasurface structure. The proposed approach opens new paths to develop flat biochemical sensors with high accuracy and real-time performance.

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Mohsen Samadi, Fatemeh Abshari, J. F. Algorri, P. Roldán-Varona, L. Rodríguez-Cobo, J. M. López-Higuera, J. M. Sánchez-Pena, D. C. Zografopoulos, and F. Dell'Olio "Refractive index sensing by all-dielectric metasurfaces supporting quasi-bound states in the continuum", Proc. SPIE 11987, Laser Resonators, Microresonators, and Beam Control XXIV, 119870B (4 March 2022); https://doi.org/10.1117/12.2608256

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