2.95 μm luminescence from a Ho3+, Pr3+ double-doped LiLuF4 optical crystal

Abstract

A Ho3+ and Pr3+ co-doped LiLuF4 single crystal was grown successfully by the Czochralski method. The polarized absorption spectra of the as-grown crystal have been investigated as a promising material for ∼2.95 μm lasers. Based on the Judd–Ofelt theory, the spectral parameters of Ho3+ in the as-grown crystal were investigated in detail. Moreover, the emission probabilities and branching ratios for Ho3+ transitions from the excited state manifolds to the lower-lying manifolds were also calculated. The stimulated emission cross-sections of the 5I6 → 5I7 transition were calculated by using the Fuchtbauer–Ladenburg (FL) method. The fluorescence lifetime of the 5I6 and 5I7 manifold were measured with a value of 1.47 and 1.97 ms, respectively. It shows that Pr3+ ions depopulate the Ho3+: 5I7 level and have little influence on the Ho3+: 5I6 level at the same time, benefiting the possible population inversion for Ho3+: 5I6 → 5I7 transition.