Growth, structural, optical and thermal properties of Yb-doped and Yb-Mg codoped LiNbO_3 single crystals

摘要

Yb-Mg codoped LiNbO_3 (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 (MgYb_(0.8) and MgYb_(1.2)) 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 Yb~(3+) 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. Yb~(3+) doping apparently decreases the Curie temperature T_c. The thermal conductivity of Yb-Mg codoped LiNbO_3 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 Yb~(3+) 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.