Acoustic metasurfaces can reshape a reflected wavefront rather arbitrarily, despite being much thinner than the wavelength, thus allowing on-demand wavefront modulation in a variety of applications.Recent passive metasurfaces, however, have suffered from bandwidth limitations, thus restricting their range of operation.In this work, we propose the systematic design of ultra-broadband passive metasurfaces by combining the broadband local reflection Ball - Catcher - Accessories rule with an optimization method.The validation of the technique is demonstrated by fabrication and measurement of an ultra-broadband carpet cloak.Numerical and experimental results show that the relative bandwidth of the optimized carpet cloak, thinner than one fifth of the maximum wavelength, can exceed 93.
33%, a value that is much larger than that of previous passive metasurfaces.Furthermore, multi-frequency pulse incidence tests reveal the excellent time-domain broadband characteristics of the metasurface over a wide range of angles of incidence.The proposed strategy opens a new route for the design of advanced passive metasurfaces for ultra-broadband AEG BP831660KM Electric Single Multifunction Oven wave manipulation and thus promotes practical applications of broadband acoustical devices.