Yb-doped LiGd1−xLux(WO4)2 single crystal fibers grown from the melt and optical characterization

• We have determined the solid solution limit of the Yb3+-doped LiLuxGd(1−x)(WO4)2 system.
• New crystals for x=0.025–0.10–0.20 were grown from a Micro pulling Down method.
• Structural, Raman, and optical characterization were performed.

As a function of lutetium concentration, Yb(1 at%)-doped LiGd1−xLux(WO4)2 phases have been synthesized by solid state reaction. For x≤0.025, a limited solid solution corresponding to the substitution of Gd3+ by Lu3+ in LiGd(WO4)2 compound was observed. In another hand, for x≥0.8 a limited solid solution corresponding to the substitution of Lu3+ by Gd3+ in LiLu(WO4)2 was obtained. Different single crystalline fibers belonging to the Yb (1 at%)-doped LiGd1−xLux(WO4)2 system with diameter average 600 µm and length up to 30 mm have been grown by micro-pulling down method. In the stationary stable growth regime, the crystallization interface was flat and meniscus length reaches 120 µm±20. An overheating of the melt causes a strong Li2O loss and composition change in the equilibrium diagram allowing growth instabilities and crystal disconnection from the molten zone. The optical characterizations have been performed. Decay time has been recorded for the 1 at% Yb3+ doped fibers.