Near-stoichiometric Lithium Niobate Crystal Growth And The Nature Of Research

crystal is a mutifunctional crystal, possessing non-linear, electrooptic, piezoelectric, photorefractive and self-frequency-doubling(SFD) properties. The congruent LiNbO₃ crystal with large size can be grown by the Czochralski method. In addition, the crystal is easy to be cut and polished for the fabrication of related elements due to its excellent mechanical property. So LiNbO₃ crystal is an important functional material, which has been extensively applicated in different fields. In recent years, stoichiometric LiNbO₃ (SLN) crystal has attracted much attention. Compared with the defect density of congruent LiNbO₃ (CLN) crystal, the defect density in SLN obviously decreases. In the meantime, many functional properties of SLN are better than those of CLN. Therefore, the crystal growth of high quality near-stoichiometric LiNbO₃ (N-SLN) is becoming a research hot point and it was expected that the SLN is of great significance and has huge market foreground. In this thesis, we focused on the crystal growth, determination of composition, observation of defects and basic properties of N-SLN crystals. However, N-SLN crystal often shows a low optical damage threshold, therefore, the Mg:SLN crystal was grown simultaneously. The main contents of this thesis is described as follows: 1. Crystal GrowthOn the basis of the crystal growth methods of SLN in this field, we choose a large crucible to grow a small SLN crystal so that the composition was kept homogeneity in crystal. The N-SLN crystal was grown from a rich lithium melt by Czochralski method. Free-cracked near-stoichiometric LiNbCh single crystals with high optical quality were successfully grown along z-axis direction.The factors that affect quality of crystals during the growth were analyzed, according to the theories of thermodynamics and dynamics of crystal growth. A suitable thermal field was designed and constructed to grow N-SLN crystals. In our understanding, the optimal thermal field and high quality seed are the prerequisite for the crystal growth with high perfection.