Transverse modes in STW resonators on quartz

Surface Transverse Wave (STW) resonators exhibit transverse modes unusually situated on the left side of the main resonance. Moreover, the quality of waveguiding can significantly affect the presence and magnitude of the transversal STW modes. Thus, propagation properties of the busbars further determines the acoustic field distribution across the resonator aperture. Here we propose a study on the properties of the transversal modes present in STW resonators with wide range of apertures. Various one-port STW resonators were manufactured, measured and analyzed. FEM simulations employing 2D FEMSAW and 2D/3D COMSOL are further used to explore the nature of the observed transversal resonances. Busbar topology with significantly improved waveguiding effect at narrower apertures is theoretically predicted and experimentally confirmed.