Light-Induced Reversible Broadening of Ferroelectric Domain Walls

Abstract Ferroelectric domain walls are active nanoscale interfaces whose functionality is governed by their internal structure rather than solely by their position. While optical stimuli are known to induce domain-wall motion, their impact on the spatial configuration of the domain-wall region remains unexplored. Here, we demonstrate that visible light induces a reversible and intensity-dependent broadening of ferroelectric domain walls in BaTiO3 crystals. Using confocal Raman microscopy, we resolve the evolution of the Raman-defined interfacial region and show that illumination transforms its spectroscopic signature from a relatively sharp boundary into an extended, graded interface. This broadening is associated with a continuous modification of the Raman response across the interfacial region and is fully reversible, with no evidence of irreversible structural changes. Our results reveal that domain walls can be dynamically reshaped by light, establishing optical excitation as a noncontact route to control the internal structure of ferroic interfaces and their associated functionalities.