Surface acoustic wave trapping in a periodic array of mechanical resonators

The existence of two families of surface acoustic modes trapped by steep ridges on a piezoelectric substrate, shear horizontal and vertically polarized surface modes, is demonstrated experimentally using high aspect ratio interdigital transducers fabricated on lithium niobate. The experimental variation of the resonance frequencies of the various surface modes is obtained experimentally, and up to an order of magnitude slowing of surface waves is observed, with the phase velocity dropping from 4000 down to 450m∕s. It is argued that the observed resonances are surface modes trapped by the ridge electrodes.