Optical absorption and luminescence of Ho3+ ions in Bi2TeO5 single crystal

Bi2TeO5:Ho single crystals were grown by the Czochralski technique. Optical absorption spectra of Ho3+ have been monitored in the 4500–25,000 cm−1 spectral and 9–300 K temperature range by high resolution Fourier Transform Spectroscopy. Luminescence excitation and emission spectra were measured at room temperature in the visible range. The intra-configurational f–f transitions of Ho3+ were identified. The experimental absorption data were analyzed by a single-ion model, and the crystal field parameters for a C2-symmetry site were determined. On the basis of these calculations and analogy with the case of Er-doped Bi2TeO5, it can be inferred that Ho–Bi substitution mostly takes place at the Bi(1) sites. The Judd–Ofelt analysis was performed by fitting the polarized absorption spectra. The calculated Judd–Ofelt parameters were used to evaluate the Ho3+ radiative transition probabilities and the branching ratios. The results are discussed in view of potential applications of Bi2TeO5:Ho3+ as a laser material.