Observation of surface-guided waves in holey hypersonic phononic crystal

Abstract

We observe experimentally the propagation of surface-guided waves in a hypersonic phononic crystal, both in the radiative and nonradiative regions of the spectrum. Combining electrical measurements in reflection and transmission as well as optical maps of the surface displacement, a band gap extending from 0.6 to 0.95 GHz is identified in a square lattice array of 1 μm radius air holes milled in lithium niobate. The optical measurements reveal the transmission of surface-guided waves above the band gap, well inside the sound cone.