Polarized spectroscopic properties of Ho3+-doped LuLiF4 single crystal for 2 μm and 2.9 μm lasers

Polarized spectroscopic properties of a Ho3+-doped LuLiF4 (Ho:LuLF) single crystal grown by the Czochralski method have been investigated as a promising material for 2 μm and 2.9 μm lasers. The Judd–Ofelt (J–O) model has been applied to the analysis of the polarized room temperature absorption spectra to establish the so-called J–O intensity parameters. Based on the calculated parameters, we determined the emission probabilities, branching ratio and radiative lifetime for the Ho3+ transitions from the excited state manifolds to the lower-lying manifolds. Ho:LuLF crystal shows long fluorescence lifetime of 5I7 manifold (16 ms) and broad absorption and emission spectra, which exhibit strong polarization characteristics. Stimulated emission cross-sections spectra of the 5I6 → 5I7 and 5I7 → 5I8 transitions were derived and compared with those of the other well-known Ho3+-doped laser crystals.

► A 1at.% Ho3+-doped LiLuF4 single crystal with high optical quality was successfully grown by Czochralski method. ► Polarized spectroscopic properties of this crystal were investigated systematically. ► The emission properties of the 5I6 → 5I7 transition of this crystal were studied for the first time to our knowledge.