Synthesis and characterization of KY₃F₁₀:Yb:Nd:Tm crystals

Energy transfer processes that generate thulium blue and ultraviolet emissions by upconversion were studied in KY₃F₁₀:Tm (KY3F:Tm), using Nd³⁺ and Yb³⁺ as sensitizers of Tm³⁺. The upconversion mechanisms were determined by exciting into the Nd and Tm absorption bands with a diode laser at 797nm. It was observed that the intensity of the Tm³⁺ blue and ultraviolet emissions in 484, 453, 366 and 350 nm were very dependent of the Yb³⁺ concentration in the samples, confirming that the main energy transfer processes involve Nd³⁺ and Yb³⁺ ions. KY₃F₁₀:Nd (1.3 mol%):Tm (0.5 mol%) crystals codoped with 5, 10, 20 and 30 mol% Yb were prepared by slow cooling from the melt, to establish the optimal Yb concentration that maximizes the Nd³⁺→Yb³⁺→Tm³⁺ energy transfer.