Slow vibration via acoustoelastic coupling: Quasi-bound states in the continuum

Abstract

Elastic bound states in the continuum (BICs) have recently garnered significant attention due to their remarkably high Q-factor, leading to the decoupling of the confined mode from spectrally coexisting radiational channels. In this presentation, we introduce a novel state capable of generating a slow vibration phenomenon, exhibiting multiphysics analogous to the concept of slow light observed in electromagnetically induced transparency (EIT). This state arises from the interaction of acoustoelastic coupling within a composite structure, featuring two acoustic cavities enclosed in an elastic bar. The proposed design facilitates quasi-BICs with exceptional spatial efficiency localized within a specific area, enabling tuning of the Purcell factor by approximately six orders of magnitude. The findings of such quasi-BICs may expand the BIC family and opens new avenues for applications in diverse fields, including lasing, sensing, screening, and energy storage platforms, where ultrahigh-Q-factor modes coexist with radiative channels.