Anti-Stokes Luminescence in BaY2F8 Crystals with Coactivation by Tb3+ and Yb3+ Ions

Spectral-kinetic characteristics of BaY2F8:Tb3+–Yb3+ in anti-Stokes luminescence processes with excitation at a wavelength of 980 nm were studied. Luminescence occurs up to UV range at transitions 5D3 → 7Fj (j = 4, 5, 6) due to energy transfer processes from ytterbium ions to terbium ions and multiphoton excitation. The power index of the dependence of the luminescence intensity on the power of the pulse excitation was measured, which is equal to 2.27 and 2 for the 5D4 and 5D3 levels, respectively. The quantum yield of anti-Stokes luminescence of crystals with coactivation by Tb3+–Yb3+ ions was measured, which is equal to 0.004, 0.03 and 0.014% for, respectively, 2, 5 and 10 at % concentration of ytterbium ions.