Enhanced luminescence at 2.7 μm of Na5Lu9F32 single crystals co-doped Er3+/Pr3+ grown by Bridgman method

Abstract

Na₅Lu₉F₃₂ single crystals co-doped with 1 mol. % Er³⁺ and various concentrations (0.1 mol. %, 0.3 mol. %, 0.5 mol. %, 0.7 mol. %, and 1 mol. %) of Pr³⁺ were successfully grown using the Bridgman method. Optical spectroscopic investigations of the obtained single crystal were reported for the absorption, emission, and luminous decay. The obtained single crystal appears with almost no absorption at the 2.7 μm band, attributable to the OH^- bond. According to the Judd-Ofelt (J-O) theory, the J-O intense parameters of Er³⁺ ions were calculated. Under the 980 nm LD pumping, an obviously enhanced emission at 2.7 μm was obtained in the Er³⁺/Pr³⁺ co-doped crystal compared with the Er³⁺ singly doped crystal due to the energy transfer from Er³⁺ to Pr³⁺. The most intense emission at 2.7 μm was obtained when the doping concentrations of Er³⁺ and Pr³⁺ were 1 mol. % and 0.5 mol. % in the present research. The maximum emission cross-section and gain cross-section at 2.7 μm were also estimated. Moreover, using the Dexter theory, the energy transfer microscopic parameters have been calculated, and the decay curve fitting using the Inokuti-Hirayama expression indicated the dipole-dipole energy transfer from Er³⁺ to Pr³⁺ ions.