Acoustic Bragg mirrors and cavities made using piezoelectric oxides

The concept and design of acoustic Bragg mirrors and cavities made of multilayers of piezoelectric oxides with superior acoustic performance and potential applications in electronic and optical terahertz modulators are described. With these applications in mind the authors have grown phonon mirrors consisting of $BaTiO3∕SrTiO3$ superlattices on $SrTiO3$ substrates by reactive molecular-beam epitaxy and investigated their properties. Characterization of the superlattices by x-ray diffraction and high-resolution transmission electron microscopy reveals high structural quality with nearly atomically abrupt interfaces. The authors have observed folded acoustic phonons at the expected frequencies using uv Raman spectroscopy.