Pingsheng Zhang

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

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.

Optical characteristics of ZnO single crystal grown by the hydrothermal method

ZnO single crystals have been grown by the hydrothermal method. Raman scattering and Photoluminescence spectroscopy (PL) have been used to study samples of ZnO that were unannealed or annealed in different ambient gases. It is suggested that the green emission may originate from defects related to copper in our samples.