Spurious modes related to the slow shear mode in an X-cut lithium tantalate crystal are suppressed and/or eliminated by reducing the ratio of plate dimension along the slow shear direction (y') to the dimension along the X direction. Undesired modes associated with the flexural family of modes can be separated in frequency from the desired, fast shear mode by the "proper" ratio of plate dimension along the fast shear direction (z') to the dimension along the X axis.
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