||Time-domain imaging of gigahertz surface waves on an acoustic metamaterial
Otsuka, Paul H. ,
Mezil, Sylvain Matsuda, Osamu ,
Tomoda, Motonobu ,
Maznev, Alexei A. ,
Gan, Tian ,
Fang, Nicholas ,
Boechler, Nicholas ,
Gusev, Vitalyi E.Wright, Oliver B.
20p.13026 , 2018-01-22 , IOP Publishing
We extend time-domain imaging in acoustic metamaterials to gigahertz frequencies. Using a sample consisting of a regular array of similar to 1 mu mdiameter silica microspheres forming a two-dimensional triangular lattice on a substrate, we implement an ultrafast technique to probe surface acoustic wave propagation inside the metamaterial area and incident on the metamaterial from a region containing no microspheres, which reveals the acoustic metamaterial dispersion, the presence of band gaps and the acoustic transmission properties of the interface. A theoretical model of this locally resonant metamaterial based on normal and shear-rotational resonances of the spheres fits the data well. Using this model, we show analytically how the sphere elastic coupling parameters influence the gap widths.