Generation and remote detection of THz sound using semiconductor superlattices

The authors introduce a novel approach to study the propagation of high frequency acoustic phonons in which the generation and detection involves two spatially separated superlattices $\sim 1 {\rm \mu m}$ apart. Propagating modes of frequencies up to $\sim 1 {\rm THz}$ escape from the superlattice where they are generated and reach the second superlattice where they are detected. The measured frequency spectrum reveals finite size effects, which can be accounted for by a continuum elastic model.