Frequency-Scaling Acoustic Resonators into mm-Wave Using Periodically Poled Piezoelectric Thin-Film Lithium Niobate

Recent studies have aimed to reproduce the success of acoustic resonators at sub-6GHz at higher frequencies, eg into mm-waves. However, such frequency scaling calls for innovation from both the material-level development and device-level design. In this talk, we will examine the fundamental limits of mm-wave acoustic resonators, then showcase transferred thin-film lithium niobate (LiNbO3) as a promising platform. More specifically, periodically poled piezoelectric film (P3F) LiNbO3 will be used for frequency scaling without losing quality factor (Q) or electromechanical coupling (k²). Finally, we will report the recent demonstration of a 50.25GHz resonator with a high electromechanical coupling (k²) of 4.5% and 3dB quality factor (Q) of 182, collectively enabling a record-breaking figure of merit (FoM, Q·k²) of 8.2, an order of magnitude higher than the state-of-the-art acoustic resonators at the same frequency.