Luminescent characteristics at ∼2.9 μm in Lu3+ modified Dy3+/Tm3+ co-doped LiYF4 single crystal

The single crystals specimens comprising 0.3 mol% Dy 3+ , 0.5 mol% Tm 3+ and γ mol% Lu 3+ doped LiYF 4 (γ = 0, 0.3, 0.5, and 1.5) were meticulously synthesized using the Bridgman method , with the specific aim of catering to applications in the ∼2.9 μm laser domain. The microstructure of the obtained single crystal was investigated by conducting X-ray diffraction (XRD) measurements. The Judd-Ofelt (J-O) intensity parameters of the Dy 3+ ion and the impacts of Lu 3+ doping on fluorescence characteristics of the 6 H 13/2 (Dy 3+ ) level were studied. The Dy 3+ /Tm 3+ doped LiYF 4 single crystal exhibits ∼52 % enhancement in emission intensity at ∼2.9 μm (Dy 3+ : 6 H 13/2 → 6 H 15/2 ) through a favorable introduction of Lu 3+ ions into the single crystal at 808 nm LD excitation. The Tm 3+ /Dy 3+ /Lu 3+ triply doped single crystal exhibited a maximum emission cross section of 2.480 × 10 −20 cm 2 at 2904 nm. The fluorescent lifetimes of the Dy 3+ : 6 H 13/2 level in the single crystals were determined to be located in the range of 2.78 ms–3.33 ms. The microscopic mechanism of energy transfer (ET) between Tm 3+ and Dy 3+ ions were investigated and the ET coefficients from 3 H 4 level of Tm 3+ ion to 6 F 5/2 of Dy 3+ ion (ET1) and 3 F 4 of Tm 3+ to 6 H 11/2 of Dy 3+ (ET2) in the triply doped single crystal were calculated, yielding values of 3.422 × 10 −39 cm 6 /s and 5.768 × 10 −39 cm 6 /s, separately. The results clearly demonstrated that the mid-infrared luminescence at ∼2.9 μm from Dy 3+ ions can be significantly enhanced by the strategic incorporation of appropriate Lu 3+ ions into Tm 3+ /Dy 3+ : LiYF 4 single crystal.