Phase transformation under direct laser writing in a YAG single crystal

The transformation from Y 3 Al 5 O 12 to perovskite YAlO 3 crystal phase was observed during ultrafast laser writing in the bulk of a Y 3 Al 5 O 12 single crystal. The control of the phase transformation was demonstrated by tuning parameters of laser writing. The phenomenon is interpreted in terms of structural changes in the overheated garnet melt under laser heating followed by rapid solidification, and at least 1-ms dwell time of overheated melt is required to start spontaneous crystallization. The appearance of the perovskite phase was confirmed by Raman spectroscopy, quantitative phase and polarization microscopies.