Abstract
Abstract
Transverse spurious modes in Lamb wave resonators (LWRs) introduce passband ripples and degrade the quality (Q) factor, limiting their potential in filter applications. Here, we demonstrate spurious-free, transverse piston-mode aluminum nitride (AlN) LWRs enabled by quasi-symmetric multi-segment electrodes. This structure is designed through a physics-guided design workflow that couples 2-D transverse dispersion theory with efficient 3-D finite-element simulations based on hierarchical cascading techniques. The fabricated 542 MHz LWR exhibits a spurious-free response and a maximum Bode-Q of 3001, nearly twice that of conventional LWRs (1672), while maintaining a comparable electromechanical coupling coefficient (kt2). Furthermore, a ladder-type filter was fabricated, with a minimum insertion loss of 2.9 dB, and an out-of-band rejection exceeding 27 dB. Notably, the measured passband is smooth with little in-band ripples, validating the effective suppression of transverse spurious modes. These results establish a practical route for integrating high-performance, spurious-free LWRs into single-chip, multi-band acoustic filters.