Pure, low loss Lamb wave transducer

A new type of pure mode Lamb wave transducer was fabricated. Between LiNbO3 wafer and glass plate, there was an interdigital transducer (IDT) with the periodicity equal to the required Lamb wavelength. The IDT generates both longitudinal and shear waves into glass. The principle is to choose the cut orientation of LiNbO3 in order that the excited bulk waves are similar to the composition of Lamb wave. As a result, most of the excited energy from transducer transfers to the selected mode, and transduction loss becomes very low. By this method we obtained the pure mode Lamb wave transducer with the lowest loss there has ever been. Between two bidirectional transducers, the insertion loss was about 12 dB