Acoustic surface waves on three-dimensional groove gratings with sub-wavelength thickness

Spoof surface acoustic waves (SSAWs) can be tightly confined at the subwavelength scale by groove gratings and propagate along the surface with low loss in a broad bandwidth. Here, we put forward a three-dimensional SSAW waveguide with a compact cross section perpendicular to the propagation direction. By introducing an additional transition part for mode conversion, the proposed SSAW waveguide can guide surface modes in a wide frequency range under the excitation of a point source. Both numerical and experimental results confirm the validity of the proposed design, thus offering attractive prospects for acoustic surface wave applications. (C) 2018 The Japan Society of Applied Physics