Growth and optical properties of Ho3+:NaGd(MoO4)2 crystal

The Ho3+:NaGd(MoO4)2 crystal with dimensions of Ф12 × 42 mm2 has been grown by Czochralski (CZ) method. Polarized absorption and fluorescence spectra at room temperature were investigated. The largest absorption cross-sections, corresponding to 5I8 → 5G6 + 5F1 absorption bands, are 31.0 × 10−20 cm2 and 23.8 × 10−20 cm2 for π- and σ-polarization, respectively. The strongest emission corresponding to the 5S2 + 5F4 → 5I8 transition can be induced by populating any higher energy level of Ho3+ ion. The fluorescence lifetimes at room temperature are 3.4 μs at 550 nm, 3.5 μs at 754 nm and 46.4 μs at 1193 nm, corresponding to transitions 5S2 + 5F4 → 5I8, 5S2 + 5F4 → 5I7, 5I4 → 5I8, and 5I6 → 5I8, respectively. Due to the influence of fluorescence trapping, the measured fluorescence lifetimes of 550 and 1193 nm should be longer than their actual values. Based on the Judd–Ofelt (J–O) theory and polarized absorption spectrum, the spontaneous transition probabilities, the fluorescent branching ratios and the radiative lifetimes were calculated.