In constructing acoustical systems, the transducer factor is one of the most essential issues. An interdigital transducer (IDT) is widely used as the most fundamental component in surface acoustic wave (SAW) technology [1, 2]. The IDT is also able to operate effectively as a leaky wave transducer at a liquid-solid interface [3-6]. The leaky wave is mode converted into a longitudinal wave into the liquid. Under the existence of liquid, the IDT is valid for controlling the radiation direction of the ultrasound, and also for operating at multiple frequencies.

A thickness mode transducer is generally used for the excitation of the longitudinal wave into the liquid [7-9].  The transducer performance is fundamental for designing practical devices. In this paper, two types of leaky wave transducers, a leaky Lamb wave transducer and a leaky Rayleigh wave transducer are described along with the applications to acoustical imaging , acousto-optic devices and liquid state sensing.