The comparison on the deactivation effects of Sm3+ and Pr3+ in Yb3+/Ho3+:CaYAlO4 disordered crystals for enhanced ∼3 µm mid-infrared laser

Abstract

Yb³⁺/Ho³⁺/Sm³⁺:CYA and Yb³⁺/Ho³⁺/Pr³⁺:CYA disordered crystals have been successfully grown by Czochralski method for the first time. To compare the deactivation effects of Sm³⁺ and Pr³⁺ for Ho³⁺ ∼3 µm mid-infrared spectroscopic characteristics, the absorption spectra, fluorescence emission spectra and fluorescence decay lifetimes are studied in detail, as well as the energy transfer mechanism. When Sm³⁺ and Pr³⁺ ions are co-doped into Yb³⁺/Ho³⁺:CYA crystal, the mid-infrared emission around 2.86 μm are significantly enhanced by 2 times and 5 times, respectively. While, the up-conversion and 2.0 μm emission intensity are obviously weakened. The fluorescence lifetime results indicate that Sm³⁺ and Pr³⁺ ions doping has a significant deactivation effect on both the upper and lower energy levels of the Ho ∼3 µm emission, which demonstrates excellent deactivation effects. The lifetimes of the Ho³⁺:⁵I₇ lower energy level in triple doped crystals reduce from 6.88 ms to 0.395 and 0.298 ms, and the energy transfer efficiencies are 94.26% and 95.67%. The lifetimes of Ho³⁺:⁵I₆ upper laser energy level reduce from 0.184 ms to 0.114 and 0.154 ms, respectively. It can be clearly seen that compared with Sm ions, Pr ions doping has a greater deactivation effect on the lower energy level and maintains a higher upper energy level lifetime, which will be more beneficial for population inversion and ∼3 μm mid-infrared laser output.