The 1.2 and 2.0 μm Emission from Ho3+ in Glass Ceramics Containing BaF2 Nanocrystals

Ho3+ and/or Yb3+ doped glass ceramics containing spherical BaF2 nanocrystals sized 10-20 nm were prepared by melt quenching and subsequent thermal treatment. Radiative properties such as transition probabilities (A), radiative lifetimes (tau), branching ratios (beta) along with absorption and emission cross sections have been calculated from the absorption spectra. Upon 637 nm excitation, Ho3+-doped glass ceramics yield an intense infrared emission at 1191 nm with a full-width at half-maximum of 80 nm and weaker emissions at 980 and 1473 nm. Efficient 1.2 and 2.0 mu m infrared emissions have been achieved in Ho3+/Yb3+ co-doped glass ceramics under 980 nm excitation, demonstrating the occurrence of energy transfer (ET) from Yb3+ to Ho3+. The microscopic parameters of the ET processes between Yb3+ and Ho3+ have been evaluated, revealing that the forward ET Yb3+ -> Ho3+ is more efficient than the backward one and both the processes are mainly assisted by one-phonon emission (annihilation).