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

This paper shows that the bulk wave that is radiated to the inside of the s ubstrate in the excitation and propagation of a leaky surface acoustic wave (LSAW) can be suppressed by forming a proton-exchanged layer on the surfac e of the substrate. It is theoretically shown that, even if the electrical condition of the propagation path is a free surface, the particle displacem ent distribution of the LSAW particle is concentrated at the substrate surf ace 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 degrees Y-X LiNbO3 substrate , and it is shown that the bulk wave can be reduced to zero by proton excha nge. It is shown experimentally that the leak loss in the propagation due t o the bulk wave radiation can be reduced to approximately one-third by the proton exchange. (C) 1999 Scripta Technica.