Broadband transmission enhancement of acoustic waves through a hybrid grating

We report an anomalous transmission enhancement of acoustic waves through a hybrid grating. The fundamental physics behind this phenomenon can be captured well by the improved impedance matching between the hybrid grating and the background fluid. This type of acoustic transparency is broadband and can be robust against the incident angle, which is drastically different from the previously reported mechanisms that are closely related with resonances. Potential applications of this effect can be anticipated in ultrasonic devices.