Enhanced ∼2.9 μm mid-infrared emissions of Ho3+/Yb3+ co-doped Na5Y9F32 single crystal introduced by Pr3+ ions

A novel Na5Y9F32 single crystals tri-doped with fixed similar to 0.8 mol% Ho3+, similar to 1 mol% Yb3+ and various Pr(3+ )from 0 to 0.8 mol% were successfully grown by a modified Bridgman method for 2.9 mu m mid-infrared application. The effects of Pr3+ ion on the 2.9 mu m emission was investigated systematically with the help of the absorption spectra, emission spectra and fluorescence decay curves. The emission intensity at similar to 2.9 mu m of Ho3+: I-5(6) -> I-5(7) was enhanced gradually as increase of Pr3+ concentration from 0 to 0.8 mol% under excitation of 980 nm laser diode (LD). The maximum emission cross-section at -2.9 mu m was calculated to be 5.62 x 10(-20) cm(2) according to the measured emission spectra. The energy transfer mechanism among Ho3+, Yb3+ and Pr3+ was studied. When the Pr(3+ )ion concentration reached 0.8 mol%, the energy conversion efficiencies for Ho3+: I-5(7) -> Pr3+ : F-3(2) and Ho3+ : I-5(6) -> Pr3+ : F-3(4) were estimated about -51.76% and -15.73%, respectively. A remarkably augmented conversion process of Ho-3(+): I-5(7) -> Pr3+ : F-3(2) by the introduction of Pr3+ ion into Ho3+/Yb3+ system results into the enhancement of similar to 2.9 mu m emission. The Pr s + ion takes as an effective deactivation of the Ho s + ion in the Na5Y9F32 single crystal. The Pr3+/Ho3+/Yb3+ tri-doped Na5Y9F32 single crystals may become a new choice for similar to 2.9 mu m mid-infrared solid-state laser due to its both excellent optical properties and chemical stability.