Observation of Two-Dimensional Acoustic Bound States in the Continuum

TL;DR

This paper reports the design and experimental demonstration of a two-dimensional acoustic resonator supporting bound states in the continuum, enabling direct measurement of pressure fields with high quality factors.

Contribution

It introduces a fully open 2D acoustic BIC design that is experimentally realizable and directly accessible, advancing the understanding of BICs in acoustic systems.

Findings

High quality factor and field enhancement observed

Direct measurement of pressure fields achieved

Symmetry-based design of BICs validated

Abstract

The design of devices based on acoustic or optical fields requires the fabrication of cavities and structures capable of efficiently trapping these waves. A special type of cavity can be designed to support resonances with a theoretically infinite quality factor, named bound states in the continuum or BICs. The experimental measurement of such modes is still a challenging problem, as they are, by definition, not accessible from external perturbations. Therefore, current reported works rely on indirect measurements that are based on the traces left by these modes on external properties of one-dimensional systems. Here we report on the theoretical design and experimental realization of a two-dimensional, fully open acoustic resonator supporting BICs. This BIC, whose symmetry is chosen during design by properly tailoring the geometrical properties of the system, is completely accessible and allows for the direct measurement of the whole pressure field and properties. We experimentally demonstrate its existence with high quality factor and field enhancement properties.