Mechanism for acoustic leakage in surface-acoustic wave resonators on rotated Y-cut lithium tantalate substrate

We discuss an acoustic loss mechanism in surface-acoustic wave resonators on 36° YX-cut lithium tantalate substrate. Recent acoustic field scans performed with an optical Michelson interferometer reveal a spatially asymmetric acoustic field atop the busbars of a resonator, giving rise to acoustic beams which escape the resonator area and lead to undesired losses. Here, we link the phenomenon with the inherent crystalline anisotropy of the substrate: the shape of the slowness curves and the asymmetry of the polarization for leaky surface-acoustic waves, propagating at an angle with respect to the crystal X-axis.