The space charge field during laser-induced domain nucleation in hafnium-doped congruent LiNbO3 crystal

The laser-induced domain nucleation effect is investigated in the 3mol% hafnium-doped congruent lithium niobate crystal. The beam from an Ar-ion laser with 514 nm wavelength is focused on z surface. Two incidence schemes are performed: (1) irradiating near and focusing on the +z surface; (2) irradiating near and focusing on the -z surface. The formed space charge field is observed by the in-situ phase mapping during the laser-induced domain nucleation. The variations of phase distributions are reconstructed by the digital holographic interferometry. The light intensity dependence of the measured photovoltaic current density j(phv) is described. The space charge field along -z direction is thought to be an important mechanism for the laser-induced domain nucleation. According to these experimental results, we present a qualitative model on the laser-induced domain nucleation process in lithium niobate crystal.