Investigation of domain inversion and internal field in congruent lithium niobate by digital holographic interferometry

摘要

The dynamic and static measurements of phase variation induced by domain inversion are performed in congruent lithium niobate crystal by the digital holographic interferometry. The existence of ridge-shape phase distribution adjacent to 180° domain wall is observed. During the domain wall motion, the phase variations are not uniform but have obvious relaxations. In the static measurement, the ridge elevation can vary linearly with the uniform electric field. The reasonable assumptions are proposed to explain these effects. The phase contrast across the crystal thickness induced by the internal field is also measured by the digital holographic interferometry just after the congruent lithium niobate crystal is partially poled. The direction of applied external field is antiparallel to that of internal field, and the measured phase contrast varies linearly with the applied external field. A new internal field is obtained by this method, and named effective internal field. The distinct discrepancy between effective and equivalent internal fields is observed. We attribute this effect to the new macroscopic representation of elastic dipole components of defect complex in the crystal.