Phase-Controlled Fano Resonances in Hybrid Metasurfaces.
basic_science · Level V
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- Record sourced from PubMed, PMID 41773652.
- Also identified by DOI 10.1021/acsnano.5c18778.
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Abstract
Quasi-bound states in the continuum (qBIC) offer high-quality factors resonances with effective far field coupling, making them ideal for applications in lasers, sensors, and nonlinear applications. We report a hybrid dielectric-metallic system that couples a qBIC with a Fabry-Pérot cavity mode, achieving tunable high-<i>Q</i> resonances through Fano interference. Using coupled-mode theory, we analytically establish the phase-dependent interaction between the discrete qBIC resonance and the continuous cavity background, revealing controllable <i>Q</i> factor, Fano asymmetry inversion, and phase singularity behavior. Coupled-mode theory further predicts that <i>Q</i> factor and Fano parameter are tunable by cavity thickness, scaling ratio of the qBIC metasurface, asymmetry, and effective refractive index. Full-wave simulations confirm the coupled-mode theory prediction, showing a maximum <i>Q</i> factor of 2.9 × 10<sup>4</sup> near the phase singularity point and revealing a rich resonance behavior through such tuning. Experimental realization in the near-infrared confirms the existence of phase singularity points and reveals a refractive index sensitivity of 732 nm·RIU<sup>-1</sup> in mixed chlorobenzene-methylaniline solutions. This work establishes a phase-tunable hybrid photonic platform for strong light-matter interaction and high-performance optical sensing.