Topology-Optimized Bound States in the Continuum with High-Q Acoustic Field Enhancement.

Achieving high-quality (high-Q) acoustic resonances remains a critical goal in acoustic device design, given their exceptional sound manipulation capabilities. However, enhancing Q-factors is often hindered by energy dissipation and material losses, except for leveraging bound states in the continuum (BICs). This paper introduces a methodology utilizing topology optimization to achieve high-Q resonances based on the concept of BICs, which effectively confine acoustic waves by minimizing energy leakage. This method explores entirely new topology classes through the optimization of a single unit cell embedded within periodic arrays. By engineering quasi-BIC modes and experimentally validating sharp pressure field enhancements, a robust technique that enables precise tuning of resonance frequencies and improves resilience against external perturbations, which is challenging for the conventional parameter-tuning approach is presented. These findings show promise for advancing wave-confining applications, such as energy harvesting and acoustic filtering, while pushing the performance boundaries of acoustic devices.