Design tradeoffs for surface acoustic wave transducers on lithium niobate

Making a surface acoustic wave transducer is often trial-and-error that requires one to balance tradeoffs between the application, performance, ease of measurement, and fabrication constraints. While one can use multi-physics simulations to gain some insight into how a transducer might perform, measured data that compares different design choices can speed up the decision-making process and even inform the simulation design space. To understand our own design tradeoffs, we designed an experiment to compare the performances of surface acoustic wave transducers where varied the metal conductors, the distances between transducers, and the number of fingers in the interdigitated transducers. We also developed a novel fabrication procedure to reduce electrical discharging that can damage electrodes. We measured the transducers with a vector network analyzer to characterize the transmission, computing the 20 dB bandwidth, resonance frequency, and insertion loss as key metrics to evaluate the device performance. Our measurements demonstrate the impact of key design parameters on the performance of LiNbO₃ surface acoustic wave transducers while the methodology, more generally provides a framework for optimizing the performance of transducers.