Acoustic guided wave devices

An acoustic wave device including piezoelectric material and electrically conductive transducer elements disposed in proximity therewith to provide acoustoelectric coupling with said device, characterized by an acoustic wave guiding volume having a thickness which is at least a significant fraction of a wavelength of an acoustic wave in said device, said wave guiding volume being disposed between two acoustic wave half spaces, each of said half spaces comprising material having an acoustic velocity which is faster than the effective acoustic velocity of the material within said wave guiding volume, said piezoelectric material and transducer elements disposed to provide acoustoelectric coupling with said wave guiding volume.