Behavior of acoustic axes and internal conical refraction in LiNbO/sub 3/ and SrTiO/sub 3/ crystals placed in an external electric field

The behavior of acoustic axes and conical refraction are analyzed for lithium niobate and strontium titanate crystals, which are either mechanically squeezed or mechanically free and placed in an external electric field. Relying on numerical calculation, field dependencies of the acoustic axis shift and splitting angles have been elaborated, which are compared with the results obtained previously in the context of the theory of perturbations. External electric fields with the intensity E<10/sup 7/ V/m have yielded small (<1/spl deg/) angles of acoustic axis splitting and shift; however, for greater field intensities, E/spl ges/10/sup 7/ V/m, the rearrangement of the crystal's acoustic axes with respect to its initial position (E=O) assumes a "macroscopic nature". In particular, degeneracies having Poincare indexes with opposite signs may merge and "annihilate". We also first examined the variation of the conical refraction parameters versus the external electric field with transverse elastic waves which propagate along the acoustic axes of conical degeneracy in the above-mentioned materials. With actually achievable field strengths, the direction of energy velocity can be altered by several degrees. It is sufficient for the development of highly effective modulators, switchers, and acoustic wave gates to be used in various logic elements and other signal processing units.