Luminescent properties of Tm^3＋/ Ho^3＋ co-doped LiYF4 crystals

Ho^3＋ with various concentrations and Tm^3＋ with molar concentration of 1.28% are co-doped in Li YF4（YLF） single crystals. The luminescent properties of the crystals are investigated through emission spectra, emission cross section and decay curves under the excitation of 808 nm. The energy transfer from Tm^3＋ to Ho^3＋ and the optimum fluorescence emission of Ho^3＋ around 2.05 μm are investigated. The emission intensity at 2.05 μm keeps increasing with the molar concentration of Ho^3＋ improved from 0.50% to 1.51% when the molar concentration of Tm^3＋ is kept at 1.28%. Moreover, for the co-doped crystals in which the molar concentrations of Tm^3＋ and Ho^3＋ are 1.28% and 1.51%, respectively, the maximum emission cross section reaches 0.760×10^-20 cm^2 and the maximum fluorescence lifetime is 21.98 ms. All the parameters suggest that these materials have more advantages in the future 2.0 μm laser applications.