On the cooling effect in the formation of periodic poled lithium niobate crystals grown by Cz technique

The effect of the cooling rate after the off-centered Cz growth process in the formation of the periodic poled lithium niobate structures has been studied. It has been observed that for a slow cooling process the periodic structures appear only at the edges of the crystals, while for a quenching to RT process the periodic structures are also formed at the center of the crystals. This fact has been related to the shape of the solid-liquid interface and the competence of the built-in internal fields created by the thermal and compositional gradient. Moreover, it has been observed that the Nb and dopant concentration along the periodic domain structure is different in both flat and convex interface.