Optical spectroscopy of zinc borate glass activated by Pr3+ ions

A zinc borate glass, 4ZnO · 3B2O3, activated by different concentrations of Pr3+ was investigated by Brillouin, Raman and luminescence spectroscopies. Energy levels and optical transitions of Pr3+ in zinc borate glass are assigned. At low Pr3+ concentration the luminescence is dominated by emission from the 1D2 state which is populated by fast multiphonon relaxation from the 3P0 state. At Pr3+ concentrations higher than 2% mol energy transfer processes become efficient in the relaxation of the 3P0 state. Cross relaxation dominates the 1D2 depopulation in the full range of Pr3+ concentrations. Self-absorption of the 3P0 -> 3H4 luminescence was observed for glassed doped with 4% and 8% mol Pr3+. Refractive index and sound velocities were measured for all the samples. Raman spectra show vibrational modes due to Pr3+ bonded to oxygen ligands.