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 o n 36 degrees YX-cut lithium tantalate substrate. Recent acoustic field scan s performed with an optical Michelson interferometer reveal a spatially asy mmetric acoustic field atop the busbars of a resonator, giving rise to acou stic beams which escape the resonator area and lead to undesired losses. He re, we link the phenomenon with the inherent crystalline anisotropy of the substrate: the shape of the slowness curves and the asymmetry of the polari zation for leaky surface-acoustic waves, propagating at an angle with respe ct to the crystal X-axis. (C) 1999 American Institute of Physics. [S0003-69 51(99)01843-4].