Phonon Bloch oscillations in acoustic-cavity structures

We describe a semiconductor multilayer structure based in acoustic-phonon cavities and achievable with molecular beam epitaxy technology, designed to display acoustic-phonon Bloch oscillations. We show that forward and backscattering Raman spectra give a direct measure of the created phononic Wannier-Stark ladder. We also discuss the use of femtosecond laser impulsions for the generation and direct probe of the induced phonon Bloch oscillations. We propose a gedanken experiment based in an integrated phonon source-structure-detector device, and we present calculations of pump and probe time-dependent optical reflectivity that evidence temporal beatings in agreement with the Wannier-Stark ladder energy splitting.