Mapping of microwave-induced phonons by μ-Brillouin spectroscopy: hypersons in ZnO on silicon

High performance Brillouin microscopy has been used as a versatile method in order to characterize the spatial distribution of piezoelectrically induced acoustic fields excited at microwave frequencies in a ZnO film deposited on silicon. Filtering properties and acoustic field distribution emitted by inter-digital transducers as well as propagation losses are investigated by μ-Brillouin spectroscopy. It turns out that the acoustic field intensity decreases dramatically outside the immediate excitation area situated below the inter-digital finger structure.