Structure, spectral properties and laser performance of Tm3+-doped Li3Ba2La3(WO4)8 crystal

Abstract

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.