EXTERNAL HOMOGENEOUS ELECTRIC-FIELD EFFECT ON THE PROPERTIES OF RAYLEIGH SAW IN LITHIUM-NIOBATE

The effect of differently oriented external electric fields on the vel ocity of Rayleigh surface acoustic wave (SAW) in LiNbO3 is theoretical ly studied for crystallographic XY, YZ, XZ planes for both mechanicall y squeezed and mechanically free crystal states. Even and odd portions of velocity variation versus the applied external electric field have been computed. The odd portion was revealed to be negative in all sit uations, metallized or not, except the XY plane for the mechanically f ree crystal with the electric field orientation normal to its surface. It is shown that the mechanical state of a crystal substantially affe cts electroacoustic interaction by varying its anisotropy and intensit y. The SAW velocity alteration is always greater for the mechanically free crystal than for the squeezed one. The surface metallization leav es the anisotropy and velocity variations essentially unchanged, excep t for the case of the XY plane and the normal field orientation. As st ated, metallized surfaces promote both slower and faster SAW velocitie s. The maximum variation of the even and odd portions of the SAW veloc ity dependence on the external electric field constitute 0.005% and 0. 2%, respectively, in the YZ and XZ planes at E = 100 kV/cm. The result s obtained correlate well with experimental data.