Influence of codoped Gd3+ ions on spectroscopic site symmetry of Dy3+ ions in LaF3 single crystal
In this paper, a series of Dy3+/Gd3+ codoped LaF3 single crystals (LDG) were grown by the Bridgman-Stockbarger method. The influence of non-optically-active Gd3+ ions on the luminescence of Dy3+ ions in LaF3 crystals has been explored. Dy3+/Gd3+ ions substitute for the La lattice in LaF3, and the local site symmetry of each subset of Dy3+ will be distorted from C2 to lower symmetry C1. Based on the measured low temperature excitation and emission spectra, it can prove that Dy3+ ions occupy the same kind of spectroscopic site in Dy3+/Gd3+ codoped LaF3 crystals, and codoped Gd3+ ions don’t change the spectroscopic site symmetry of Dy3+. When Gd3+ ions were codoped into Dy3+:LaF3 crystal, Dy-Gd clusters are formed around single Dy3+ ions to isolate Dy3+ ions from each other and weaken the concentration quenching effect of Dy3+ ions. When 2 at% Dy3+ and 1 at% Gd3+ ions were doped into LaF3 crystal, the strongest yellow luminescence were obtained under the excitation of 349 nm and 453.75 nm, respectively. While doped with 2 at% Dy3+ and 2 at% Gd3+ ions, LDG crystal got the strongest mid-infrared fluorescence emission intensity. It concludes that the LDG crystals are suitable for achieving yellow laser (4F9/2 → 6H13/2 transition) pumped by InGaN blue laser diode (LD) and mid-infrared laser (6H13/2 → 6H15/2 transition) pumped by 1280 nm LD.