Tunable collective electromagnetic induced transparency-like effect due to coupling of dual-band bound states in the continuum

TL;DR

This paper demonstrates a tunable EIT-like effect in all-dielectric metasurfaces caused by coupling dual-band bound states in the continuum, enabling control over slow light and sensing sensitivity.

Contribution

It introduces a novel tunable collective EIT-like phenomenon arising from coupling dual-band q-BICs in dielectric metasurfaces, with adjustable optical properties.

Findings

The EIT-like effect can be tuned by nanodisk size and tilt angle.

Slower light and higher sensitivity are achieved with decreasing nanodisk size.

Sensitivity exhibits exponential growth and then plateaus as the group index increases.

Abstract

The coupling between dual-band or multi-band quasi-bound states in the continuum (q-BICs) is of great interest for their rich physics and promising applications. Here, we report tunable collective electromagnetic induced transparency-like (EIT-like) phenomenon due to coupling between dual-band collective electric dipolar and magnetic quadrupolar q-BICs, which are supported by an all-dielectric metasurface composed of periodic tilted silicon quadrumers. We show that this collective EIT-like phenomenon with strong slow light effect can be realized by varying the nanodisk diameter or the tilt angle, and that the transparency window wavelength, the quality factor, and the group index can all be tuned by changing the nanodisk size. We further find that as the nanodisk size decreases, the slow light effect becomes stronger, and higher sensitivity can be obtained for the refractive index sensing. Interestingly, the sensitivity first increases exponentially and then reaches a plateau as the nanodisk size decreases, or equivalently as the group index increases. We therefore expect this work will advance the understanding of the collective EIT-like effect due to coupling between q-BICs, and the findings will have potential applications in slow-light enhanced biochemical sensing.