Judd-Ofelt modelling and stimulated-emission cross-sections for Tb3+ ions in monoclinic KYb(WO4)2 crystal

Terbium (Tb3+) ions are promising for the development of visible lasers. We report on the spectroscopy of Tb3+ in the monoclinic KYb(WO4)2 (KYbW) crystal, including the Judd-Ofelt (J-O) modelling of the transition probabilities, evaluation of the absorption and stimulated-emission (SE) cross-sections with polarized light, and emission lifetime study. Within the strong configuration interaction (SCI) approximation of the J-O theory, the intensity parameters of Tb3+ are Ω2 =0.864, Ω4 =1.657, Ω6 =1.975 [10-20 cm2] and Δ=38810 cm-1. The maximum σabs for the 7F6 → 5D4 transition reaches 2.3×10-21 cm2 at 486.7 nm and the maximum σSE for the green emission according to the 5D4 → 7F5 transition is 2.3×10-21 cm2 at 549.3 nm (both for E || Nm). The measured lifetime of the 5D4 state for a 1 at% Tb3+ doping is 395±5 μs. Under blue excitation, Tb: KYbW exhibits intense green emission with the CIE 1931 coordinates of (0.312; 0.644).