Highly Efficient Acoustic Metagrating with Strongly Coupled Surface Grooves

Acoustic metasurfaces, generally comprising several types of localized meta-atoms, draw great interest for their flexibility in acoustic field manipulation. However, the unavoidable $n\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ coupling between meta-atoms leads to lackluster performance for large-angle refraction. By embracing rather than ignoring nonlocality and periodicity, this research shows that acoustic metagratings can almost perfectly bend sound for very large angles (>80\ifmmode^\circ\else\textdegree\fi{}), with up to 95% transmission. Besides efficiency, the suitably treated nonlocality provides another degree of freedom to manipulate sound propagation, extending the realm of acoustic metasurfaces and promoting innovative techniques.