Optical properties of Ho3+-doped NaGd(WO4)2 crystal for laser materials

Holmium doped sodium gadolinium tungstate crystals with sizes of about Ø20 mm × 40 mm were grown successfully by the Czochralski technique along the (0 0 1) orientation. Polarized absorption spectra, fluorescence spectra and fluorescence decay curve of Ho3+-doped NaGd(WO4)2 have been recorded at room temperature. Based on the Judd–Ofelt theory, three intensity parameters were obtained. The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetimes as well as the branching ratios were calculated. The fluorescence lifetime τf of the 5S2 level was measured to be 5 μs.