Growth, structural, optical and thermal properties of Yb-doped and Yb–Mg codoped LiNbO3 single crystals

Yb–Mg codoped LiNbO3 (LN) crystals have many applications in self-frequency doubling lasers. However, the great difficulty associated with growing this crystal is one of the obstacles for its application. In this work, Yb-, Mg-doped and Yb–Mg codoped (MgYb0.8 and MgYb1.2) single crystals were successfully grown by the Czochralski method from the congruent melt. Some basic physical properties have been measured to provide reliable reference for application of the crystals. Compared to its value in a singly doped crystal, the effective segregation coefficient of the Yb3+ ion in codoped crystals clearly decreases. When doping Yb into Mg-doped LN, the absorption edge of the crystal shifts to longer wavelengths, while the refractive index stays nearly the same. Yb3+ doping apparently decreases the Curie temperature Tc. The thermal conductivity of Yb–Mg codoped LiNbO3 was found to be identical to that of Mg-doped LN and greater than that of congruent LN (CLN), which is a benefit for laser applications. The occupation sites of the Yb3+ ions are discussed, and the distinct raised growth ridges observed are attributed to the change in the lattice structure due to Yb–Mg co-doping.

► High quality Yb–Mg codoped LiNbO3 crystals in size of ∅50 × 40 mm were grown by the Czochralski method.
► Compared to that in Yb-doped crystal, the keff of Yb3+ ion in codoped crystals clearly decreases.
► The absorption edge of Yb–Mg codoped LiNbO3 shifts to longer wavelengths, compared to that of MgOCLN.
► The thermal conductivity of Yb–Mg codoped LiNbO3 was identical to MgOCLN and greater than CLN.
► The distinct raised growth ridges are attributed to the change in lattice structure due to Yb–Mg co-doping.