Perfect sound absorption induced by topological acoustic unidirectional guided resonance

Abstract

Perfect sound absorption (PSA) plays a vital role in various acoustic applications. Acoustic unidirectional guiding resonances (AUGRs) are a novel class of topologically enabled guided resonance that only radiates toward a single side. The symmetries and unidirectional features of AUGRs reduce the number of ports to one that simultaneously adds or drops energy. As a result, we theoretically show that with the addition of thermos-viscous losses, AUGRs can be used to achieve unidirectional PSA with single-sided illumination without the need for any backing mirrors. The good agreement between the results of temporal coupled mode theory (TCMT) and full-wave simulations confirms our findings. In the parameter space spanned by frequency and incident angle, topological spectral phase singularities (SPSs) appear and are associated with topological charges, which confirm the robustness of the PSA phenomenon against variations in structural parameters and physical conditions. Our proposed structure may contribute to the practical applications of advanced absorbers and sensors.