Investigation of Sensing and Slow-Light Based on Dual Accidental Quasi-Bound States in the Continuum
In recent years,bound states in the continuum(BIC)in optical metasurfaces have garnered significant attention owing to their unique properties.Because of the interaction of two accidental quasi-bound states in the continuum(A-QBIC)modes,we explore the related novel optical phenomena in an all-dielectric metasurface that comprises a square nano-aperture array.It is shown that the A-BIC phenomenon can occur under x-and y-polarized normal incidences but exhibits the interaction of the two A-QBIC modes under 45° polarized incidence.The A-QBIC modes,which are analyzed using band and multipole expansion theories,are primarily governed by the toroidal dipole.Notably,the high Q-factor of the A-QBIC modes not only allows for the implementation of highly sensitive refractive index sensing but also facilitates the realization of flexible tunability of the interaction between the two A-QBIC modes,thereby achieving an analogue of electromagnetically induced transparency and tunable slow-light.Our results provide a feasible strategy to develop a high Q-factor meta-device based on A-QBIC in highly sensitive refractive index sensing and slow-light applications.
all-dielectric metasurfacebound states in the continuumaccidental quasi-bound states in the continuumrefraction index sensingslow-light
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