Observation of light-induced localized domain-inversion pattern formation in KNbO₃

It is demonstrated that high-intensity illumination with an Ar-ion laser beam can generate domain-inversion patterning in KNbO₃ crystals. With a special laser-assisted micro-manipulation platform, direct patterning of domain-inversion structures without applying any external electric field can be carried out. The domain-nucleation process has been observed, and the process is purely optical, localized, and potentially controllable both in size and in orientation.