External homogeneous electric field effect on the properties ofRayleigh SAW in lithium niobate

摘要

The effect of differently oriented external electric fields on thenvelocity of Rayleigh surface acoustic wave (SAW) in LiNbO3 isntheoretically studied for crystallographic XY, YZ, XZ planes for bothnmechanically squeezed and mechanically free crystal states. Even and oddnportions of velocity variation versus the applied external electricnfield have been computed. The odd portion was revealed to be negative innall situations, metallized or not, except the XY plane for thenmechanically free crystal with the electric field orientation normal tonits surface. It is shown that the mechanical state of a crystalnsubstantially affects electroacoustic interaction by varying itsnanisotropy and intensity. The SAW velocity alteration is always greaternfor the mechanically free crystal than for the squeezed one. The surfacenmetallization leaves the anisotropy and velocity variations essentiallynunchanged, except for the case of the XY plane and the normal fieldnorientation. As stated, metallized surfaces promote both slower andnfaster SAW velocities. The maximum variation of the even and oddnportions of the SAW velocity dependence on the external electric fieldnconstitute 0.005% and 0.2%, respectively, in the YZ and XZ planes atnE=100 kV/cm. The results obtained correlate well with experimental data