Realization of inverse-designed underwater acoustic superscattering

Superscattering is a unique wave phenomenon that allows subwavelength objects to produce a large scattering cross section, surpassing the fundamental single-channel limit. This effect has been extensively studied in many wave systems, such as electromagnetic waves, water surface waves, and airborne acoustics. However, in the context of underwater acoustics, achieving superscattering with a single material has remained unexplored due to complex acoustic-solid interactions. Here, we have inversely designed a simple yet efficient structure to achieve the superscattering of ultrasound in water. Both numerical simulations and experimental results show that the proposed superscatterer exhibits significantly stronger ultrasound backscattering compared with a bare rigid cylinder. Furthermore, we construct a superscattering chain barrier. It is able to enhance ultrasound insulation while maintaining water permeability. This chain barrier is demonstrated to be robust for ultrasound with a wide range of incident angles. The results from this study are expected to benefit various fields of underwater acoustics, particularly in marine detection and sea-life protection.