Acoustic scattering singularities via quasi-Bound states in the continuum

Abstract

Non-Hermitian systems enable advanced control of wave propagation by exploiting engineered losses. This introduces an additional degree of freedom that permits the emergence of exceptional points (EPs). In this letter, we theoretically and experimentally demonstrate the control of scattering singularities in a non-Hermitian acoustic system using quasibound states in the continuum (qBICs). Through Friedrich Wintgen interference, the losses of a two port cavity are tuned until achieving critical coupling, yielding narrowband coherent perfect absorption (CPA) with a quality factor of 140. Additionally, by coupling two distinct resonators, we observe the emergence of an EP, where both eigenvalues simultaneously coalesce and vanish, resulting in narrowband unidirectional absorption. Our results establish a connection between qBICs and scattering singularities, and offer a route toward acoustic devices featuring narrowband resonances and tunable radiative losses.

References in corpus (12)

• Non-Hermitian Physics
• Non-Hermitian Topology and Exceptional-Point Geometries
• Coherent perfect absorbers: linear control of light with light
• Acoustic non-Hermitian skin effect from twisted winding topology
• Extremely asymmetrical acoustic metasurface mirror at the exceptional point
• PT-symmetric scattering in flow duct acoustics
• Non-Hermitian Acoustic Metamaterials: the role of Exceptional Points in sound absorption
• Unidirectional zero sonic reflection in passive $\mathcal{P}\mathcal{T}$ symmetric Willis media
• Elastic Bound State in the Continuum with Perfect Mode Conversion
• Coherent Perfect Absorption induced by the nonlinearity of a Helmholtz resonator
• Exact analogue of the Hatano-Nelson model in 1D continuous nonreciprocal systems
• Acoustic Bound States in the Continuum in Coupled Helmholtz Resonators