Piezoelectric Transduction of a Wavelength-Scale Mechanical Waveguide

We present a piezoelectric transducer in thin-film lithium niobate that converts a 1.7-GHz microwave signal to a mechanical wave in a single mode of a 1-μm-wide waveguide. We measure a -12-dB conversion efficiency that is limited by material loss. The design method we employ is widely applicable to transduction in wavelength-scale structures in emerging phononic circuits such as those needed for efficient piezo-optomechanical converters and spin-phonon transducers.