Influence of electrode materials and structural design on third-order nonlinear signals of SAW devices

In this paper, we investigate influence of the electrode on the third-order nonlinearity of SAW devices. First, some one-port resonators are fabricated on 42°YX-LiTaO
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substrates with different electrode material or electrode crystallinity, and their nonlinear signal levels are estimated. As the result, nonlinear signal levels change markedly with electrode material and crystallinity of electrode. Next, the electrode metal stack is redesigned not to change the linear characteristics of resonators, and its impact to the nonlinearity is estimated. From the results of these discussions, it is concluded that electrode fingers in IDT are one of the major sources of the third-order nonlinearity.