Acoustic wave devices using periodical poled Z-cut LiTaO₃ plate

Though acoustic wave devices using a periodical poled Pb(Zi_x, Ti_1-x)O₃ (PZT) ceramic plate on Si substrate, a periodical poled Pb(Zr_0.2Ti_0.8)O₃ thin film on (001)SrTiO₃ substrate, and a periodical poled Z-LiNbO₃ substrate have been reported, their frequency responses were very weak as 0.1 to 3dB. It is considered that because their periodical poled devices have neither electrode fingers of intergidital transducers (IDTs) nor grating electrode reflectors, they do not have any effective reflection to realize a good frequency response, while conventional SAW devices have them. This time, authors have proposed an effective reflector for the periodical poled substrate device and applied it to a resonator and a resonator filter using a periodical poled Z-plane LiTaO₃ plate, which is different from previously reported substrates. As the result, authors realized the resonator and the resonator filter having good frequency characteristics such as an impedance ratio of 33dB, and an insertion loss of 2.6 dB and a relative bandwidth of 2.2 %, respectively, for the first time.