Acoustic wave devices composed of periodically poled Z-cut LiTaO ₃ plate using edge reflection

The excitation method using the periodically poled (PP) structure has several merits suited for high-frequency devices in comparison with the excitation method using a conventional interdigital transducer (IDT). For example, a simple photolithography process, absence of short circuit caused by metallic powder, and a strong electric power durability can be expected. Although transducers using PP plates or PP films have been reported, none of the resonator-type devices using them has been. The authors attempted to fabricate PP resonators and resonator filters by applying an edge reflector to the fabrication of PP structure devices. As the result, a resonator having an impedance ratio of 33 dB and a resonator filter having an insertion loss of 2.6 dB and a relative 3 dB bandwidth of 2.2% were realized.