Compact asymmetric sound absorber at the exceptional point

We present an asymmetric absorber at an exceptional point (EP) with a compact configuration and deep-subwavelength thickness. Unlike conventional side-branched sound absorbers in dual-port systems, the proposed asymmetric absorber exhibits a compact shape that is coaxial with the waveguide. By tuning the loss and geometric parameters of the non-Hermitian system to reach an EP, we observe extreme asymmetric absorption. This phenomenon is theoretically and experimentally validated by observing a quasi-perfect absorption and a near-total reflection for opposite incidences at the ultra-thin (1/28th of the operating wavelength) neck-embedded tube employed in this study. Furthermore, we demonstrate an EP-induced tunable asymmetric absorption. Our study proposes novel approaches to manipulate the EP-induced wave phenomena, paving the way for the development of novel acoustic absorbers, sensors, isolators, and directional devices.

Automated summary

This study presents an asymmetric absorber at an exceptional point with a compact configuration and deep-subwavelength thickness, which exhibits extreme asymmetric absorption. By tuning the loss and geometric parameters to reach an EP, the system shows interesting absorption phenomena.