Growth, structure, and spectroscopic properties of a Cr3+, Tm3+, Ho3+, and Pr3+ co-doped LuYAG single crystal for 2.9 μm laser

Abstract

A new laser crystal from Lu_2.4Y_0.6Al₅O₁₂ (LuYAG) co-doped with Cr³⁺, Tm³⁺, Ho³⁺, and Pr³⁺ ions was grown successfully by the Czochralski method for the first time. The structure parameters of the Cr,Tm,Ho,Pr:LuYAG crystal are determined by the X-ray Rietveld refinement method. The main absorption bands are observed near 426 and 782 nm, and the fluorescence spectrum excited by a 450 nm or 783 nm LD presents an emission band near 2.911 μm, indicating that the co-doped Cr³⁺ and Tm³⁺ ions can be utilized as sensitizers for the Ho³⁺ ions. The lifetimes of the ⁵I₆ and ⁵I₇ levels of the Ho³⁺ ions were measured and fitted to be 0.070 ms and 1.852 ms, respectively. The energy transfer efficiencies of the processes ⁵I₆ (Ho³⁺) → ³F_3,4 (Pr³⁺) and ⁵I₇ (Ho³⁺) → ³F₂ (Pr³⁺) + ³H₆ (Pr³⁺) were calculated, showing that the Pr³⁺ ions can play the role of a deactivator for the Ho³⁺ ions. Furthermore, the energy transfer mechanisms among the Cr³⁺, Tm³⁺, Ho³⁺, and Pr³⁺ ions were studied. The results suggest that the Cr,Tm,Ho,Pr:LuYAG crystal is a new promising laser medium operating at around 2.9 μm under flash lamp or 783 nm LD pumping.