Anomalous diffractions of water waves in parity-controlled metagratings

Owing to the formal analogy between their governing equations, concepts from electromagnetic wave physics have been successfully extended to water-wave systems. Here, we propose and experimentally demonstrate the water-wave metagratings (WMGs) capable of wavefront modulation based on the generalized Snell’s law. These WMGs generate anomalous diffraction, including both retroreflection and negative refraction, by engineering the integer parity of supercells. As a proof of concept, we realize broadband water-wave focusing using WMGs. This work opens new avenues for compact and tunable water-wave devices, with potential applications in wave-energy harvesting and marine engineering.