Reduced phase-matching temperature in magnesium-doped lithium niobate crystals grown from ternary MgO–Li 2 O–Nb 2 O 5 system

Abstract As a classic frequency-doubling crystal for the visible spectra range, heavily magnesium-doped lithium niobate (LN:Mg) has long been hindered in its application to compact and thermally stable laser systems by its intrinsically high phase-matching temperature. In this study, a series of MgO-doped LiNbO 3 crystals were grown from the ternary MgO–Li 2 O–Nb 2 O 5 system, and their optical and nonlinear optical properties were systematically characterized. Compared with crystals grown from the conventional congruent binary Li 2 O–Nb 2 O 5 system, the as-grown crystals from the ternary system exhibit markedly improved optical quality, enhanced optical damage resistance, and superior frequency-doubling performance. In particular, the LiNbO 3 crystal doped with 6.0 mol.% MgO achieves an optical damage resistance threshold of 6.5 MW cm −2 , which is an order of magnitude higher than that of the 5.0 mol.% MgO-doped LiNbO 3 crystal grown from the binary system. Meanwhile, a high SHG conversion efficiency of 30.7% for a 1064 nm pulsed laser is realized at a reduced phase-matching temperature of 45.1 °C, with a corresponding temperature bandwidth of 1.5 °C. These results demonstrate that compositional modulation via the ternary system is an effective strategy to simultaneously improve the crystal quality and nonlinear optical performance of MgO-doped LiNbO 3 crystals. The greatly optimized frequency-doubling properties underscore the significant application potential of the as-prepared LN:Mg crystals as efficient frequency converters for advanced compact green laser systems.