Investigation of optical birefringence at ferroelectric domain wall in LiNbO3 by phase-shift polarimetry

We investigated the optical birefringence near the wall between two opposite domains in a z-cut congruent LiNbO3 through a full-field polarimetric method. We obtained a measure of domain wall width and determined the direction of the principal axes of stress-induced birefringence. Experimental data show that the principal axes of stress-induced birefringence result to be parallel or perpendicular to the domain wall, according to theoretical predictions. The domain wall width value ranges from 10 to about 50 micron showing a spatial variation that we can appreciate since the used method allows us to obtain two dimensionally resolved measurements.