Structure, Optical Properties and Physicochemical Features of LiNbO₃:Mg,B Crystals Grown in a Single Technological...

Two series of LiNbO₃:Mg:B crystals have been grown and studied. Two doping methods-have been used. The crystals-have been co-doped with Mg and a non-metallic dopant, B. The physicochemical features of the growth-have been considered for LiNbO₃:Mg:B crystals obtained from a boron-doped melt. The charge-has been prepared using different technologies: homogeneous (HG) and solid-phase (SP) doping. The same two methods have been used to grow single-doped LiNbO₃:Mg crystals. A control near-stoichiometric (NSLN) crystal-has been grown via the HTTSSG (high-temperature top-seeded solution growth) method from a congruent melt (Li/Nb ≈ 0.946) with 5.5 wt% K₂O. The characteristics of the LiNbO₃:Mg:B crystals-have been compared with those of the LiNbO₃:Mg and NSLN crystals. Physicochemical and structural reasons have been established for the differences in the distribution coefficients of magnesium (K_D) during the growth of the HG- and SP-doped LiNbO₃:B:Mg and LiNbO₃:Mg crystals. The optical characteristics of the LiNbO₃:B:Mg crystals-have been studied via optical spectroscopy, laser conoscopy and photoinduced light scattering (PILS). The influence of boron on the microstructure, compositional and optical uniformities and optical damage resistance of the LiNbO₃:Mg:B crystals-has been estimated. Optimal technological approaches to growing optically uniform LiNbO₃:B:Mg crystals have been determined. LiNbO₃:Mg:B crystals have been shown to have a significant advantage over the commercially used LiNbO₃:Mg crystals since large LiNbO₃:Mg:B crystals can be grown without stripes. Such stripes usually appear perpendicular to the growth axis. In addition, the photorefractive effect is suppressed in LiNbO₃:Mg:B crystals at lower magnesium concentrations ([Mg] ≈ 2.5 mol%) than in LiNbO₃:Mg ([Mg] ≈ 5.5 mol%).