Polarization state dependence of laser-induced domain nucleation in lithium niobate crystals investigated by digital holography

This paper systematically investigates the influences of polarization states on laser-induced domain nucleation in z-cut LiNbO3 crystals. The real-time 2D and 3D phase distributions at the focus during laser-induced domain nucleation were reconstructed by digital holography. The different LiNbO3 samples, including undoped congruent LiNbO3, Mg-doped congruent LiNbO3, Hf-doped congruent LiNbO3, and stoichiometric LiNbO3, were tested. The systematical comparisons of phase mapping and nucleation fields with different polarization states, including linear polarization, circular polarization, and elliptical polarization, have been carried out. The polarization states proved to be a key influence factor for the laser-induced domain nucleation. It was demonstrated that the generated bulk photovoltaic field along the -z direction was an important mechanism for laser-induced preferential domain nucleation. This work is of great significance for the future development of ferroelectric domain engineering of LiNbO3 crystals. (C) 2020 Optical Society of America