Bound States in the Continuum in Compact Acoustic Resonators

TL;DR

This paper demonstrates that finite-size solid acoustic resonators can support true bound states in the continuum, which can be classified by multipole moments and transformed into high-Q resonances through symmetry breaking.

Contribution

It introduces a theoretical framework for classifying BICs in various-shaped acoustic resonators and explores their transformation into quasi-BICs with high-Q resonances.

Findings

Finite-size resonators support true BICs localized inside.

Symmetry breaking turns BICs into high-Q Fano resonances.

Potential applications in acoustic sensors and topological structures.

Abstract

We reveal that finite-size solid acoustic resonators can support genuine bound states in the continuum (BICs) completely localized inside the resonator. The developed theory provides the multipole classification of such BICs in the resonators of various shapes. It is shown how breaking of the resonator's symmetry turns BICs into quasi-BICs manifesting themselves in the scattering spectra as high-Q Fano resonances. We believe that the revealed novel states will push the performance limits of acoustic devices and will serve as high-Q building blocks for acoustic sensors, antennas, and topological acoustic structures.