| A proton-exchanged layer with an elastically soft property can be buried into a substrate by a reverse proton exchange (RPE) process. It is expected that the RPE layer with a property similar to that of bulk LiNbO3 (LN) will prevent the degradation of the coupling factor and that the buried PE layer will reduce the leaky SAW (LSAW) attenuation. In this study, first, a layered structure of air/bulk LN/softened LN was assumed for the rotated Y-X LN and the LSAW attenuation was calculated. The rotation angle from the Y-axis giving zero attenuation shifted from 64° toward 5° for a metallized surface. The range of rotation angles at which the LSAW phase velocity exceeds that of a fast shear bulk wave was markedly expanded for a free surface, and the attenuation vanished at these boundaries. Next, the LSAW propagation loss PL was measured on 41° Y-X LN. The PL for the metallized surface was decreased by carrying out the RPE process from 0.036 dB/λ of a virgin sample to 0.015 dB/λ. The decrease of the PL for the free surface was also observed. |