Abstract
In this paper, optical spectra of LiYF4 single crystals doped with Tm3+ ions of various concentrations are reported. The emission intensity at 1.8 μm first increases with increasing Tm3+ concentration, and reaches a maximum value when the concentration of Tm3+ is about 1.28 mol%, then it decreases rapidly as the concentration of Tm3+ further increases to 3.49 mol%. The emission lifetime at 1.8 μm also shows a similar tendency to the emission intensity. The maximum lifetime of 1.8 μm is measured to be 17.68 ms for the sample doped with Tm3+ of 1.28 mol%. The emission cross section of 3F4 level is calculated. The maximum reaches 3.76 × 10−21 cm2 at 1909 nm. The cross relaxation (3H6, 3H4 →3F4, 3F4) between Tm3+ ions and the concentration quenching effect are mainly attributed to the change of emission with Tm3+ concentration. The largest quantum efficiency between Tm3+ ions is estimated to be ∼147% from the measured lifetime and calculated radiative lifetime. All the results suggest that the Tm3+/LiYF4 single crystal may have potential applications in 2 μm mid-infrared lasers.
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