Structure, spectral properties and laser performance of Tm3+-doped Li3Ba2La3(WO4)8 crystal†
A pure and a Tm3+-doped Li3Ba2La3(WO4)8 single crystal were grown by the top seeded solution growth method from Li2WO4 flux. The structure of the pure crystal was determined by the single-crystal X-ray diffraction method. It crystallizes in the monoclinic space group C2/c with a = 5.323(6) (Å), b = 13.091(15) (Å), c = 19.48(2) (Å), β = 91.18(3)°, and Z = 2. In the structure, La3+ and Li+ share the same 8f lattice site with a ratio of occupancy of 0.75 : 0.25. The high structural disorder of the Li3Ba2La3(WO4)8 crystal leads to inhomogeneous spectral broadening of Tm3+ ions contained within it, for which the absorption bands around 795 nm are broad and emission bands around 1.9 μm are smooth. Pumped by a quasi-continuous-wave diode laser at 795 nm, an output power of 3.0 W with slope efficiency of 40% around 1.9 μm was achieved in a Tm3+:Li3Ba2La3(WO4)8 crystal. The results indicate that the Tm3+:Li3Ba2La3(WO4)8 crystal is a promising gain medium for a tunable laser around 1.9 μm.