Design and implementation of mixed-mode transducers

Abstract

In order to design a mixed-mode transducer with high efficiency and broad bandwidth for both longitudinal and shear wave modes, a theory is developed to determine the properties of this transducer with arbitrary acoustic loads at both ends of the piezoelectric element. Several Y-cut lithium niobate (LiNbO(3)) transducers were made on both [110] single-crystal bismuth germanium oxide (Bi(12)GeO(20)) and fused quartz. The piezoelectric plates were attached to indium bonding and later polished to operate in the 100-MHz frequency range. The experimental data of round-trip insertion loss for both longitudinal and shear modes showed an excellent agreement with theoretical predictions.