Influence of electrode width of interdigital transducer on third-order nonlinear signals of SAW devices on 42°YX-LiTaO3 substrate

In this paper, we investigate the influence of the electrode width on the third-order nonlinearity of SAW devices fabricated on 42°YX-LiTaO₃ substrates. First, acoustic strain in Al film of electrode in interdigital transducer is calculated with respect to various electrode width using two-dimensional finite element method, and from the results, variation of third-order nonlinearity with electrode width is estimated. Then one-port SAW resonators with different electrode width are fabricated, and their third-order nonlinearities are compared with the numerically predicted results. As the result, numerical simulation predicts the variation of third-order nonlinearity well when the ratio of electrode width with respect to electrode period is larger than 0.4, while disagreements exist when the electrode width is smaller than the above case. In addition, numerical fitting are performed for the measurement results using the simulation technique for nonlinear signals, and it is concluded that the generation mechanism is not limited to acoustic strain in electrode, but other causes surely exist.