All-Optical Domain Inversion in LiNbO₃ Crystals by Visible Continuous-Wave Laser Irradiation

Abstract

LiNbO 3 is a distinguished multifunctional material where ferroelectric domain engineering is of paramount importance. This degree of freedom of the spontaneous polarization remarkably enhances the applicability of LiNbO 3 , for instance, in photonics. In this work, we report the first method for all-optical domain inversion of LiNbO 3 crystals using continuous-wave visible light. While we focus mainly on iron-doped LiNbO 3 , the applicability of the method is also showcased in undoped congruent LiNbO 3 . The technique is simple, cheap, and readily accessible. It relies on ubiquitous elements: a light source with low/moderate intensity, basic optics, and a conductive surrounding medium, e.g., water. Light-induced domain inversion is unequivocally demonstrated and characterized by combination of several experimental techniques: selective chemical etching, surface topography profilometry, pyroelectric trapping of charged microparticles, scanning electron microscopy, and 3D C ̌erenkov microscopy. The influence of light intensity, exposure time, laser spot size, and surrounding medium is thoroughly studied. To explain all-optical domain inversion, we propose a novel physical mechanism based on an anomalous interplay between the bulk photovoltaic effect and external electrostatic screening. Overall, our all-optical method offers straightforward implementation of LiNbO 3 ferroelectric domain engineering, potentially sparking new research endeavors aimed at novel optoelectronic applications of photovoltaic LiNbO 3 platforms.