Localized switching in photorefractive ferroelectrics induced by spatially inhomogeneous electric fields

We examine theoretically the stability of 180° domain patterns that may form inside photorefractive ferroelectric crystals when an optically induced spatially modulated electric field is present. By analyzing the total free energy of a ferroelectric crystal subjected to an applied field and with free charges contained within, we find under what conditions (magnitude of the applied field, amplitude of the optically induced electric field, and domain-wall energy density) the spontaneous polarization of the crystal tends to switch throughout the whole crystal and under which only partial switching occurs.