Transmission of coherent phonons through a metallic multilayer - art. no. 174304

The transmission of a coherent beam of longitudinal acoustic phonons throug h a 12-layer Ag-Au superlattice is measured with high resolution at gigaher tz frequencies. The phonons are generated with laser-induced thermomodulati on of a Au transducer and, after passage through the superlattice, detected with Brillouin scattering in the PbMoO4 single-crystalline substrate. The transmission is found to drop to about 1% in well-defined stop bands. Calcu lations based on wave equations with inclusion of acoustic damping quantita tively reproduce the stop bands as well as the oscillatory frequency depend ence of the transmission at intermediate frequencies.