Suppression of bulk wave radiation of leaky surface acoustic waves by proton exchange

Abstract

This paper shows that the bulk wave that is radiated to the inside of the substrate in the excitation and propagation of a leaky surface acoustic wave (LSAW) can be suppressed by forming a proton-exchanged layer on the surface of the substrate. It is theoretically shown that, even if the electrical condition of the propagation path is a free surface, the particle displacement distribution of the LSAW particle is concentrated at the substrate surface by proton exchange, as in the case of a metallized surface. This result suggests that the bulk wave radiation in LSAW excitation can be suppressed. The bulk wave radiation loss is examined by measuring the insertion loss between the input and the output IDT on the 41° Y-X LiNbO3 substrate, and it is shown that the bulk wave can be reduced to zero by proton exchange. It is shown experimentally that the leak loss in the propagation due to the bulk wave radiation can be reduced to approximately one-third by the proton exchange. © 1999 Scripta Technica, Electron Comm Jpn Pt 3, 83(1): 44–52, 2000