Optical spectra of erbium and thulium in germanate glass

Oscillation strengths, emission and excitation spectra and decay times of Tm³⁺ and Er³⁺ in germanite glasses were measured. The results were compared with the data obtained previously in borate and phosphate glasses. The role of glass phonons on the transition probabilities, half-width of emission bands and the Stokes shift is discussed. Also, the influence of the cavity and the site symmetry in which the rare earth is situated on transition probabilities is discussed. Bands in the emission spectrum of Er³⁺, absent in the borate and phosphate, are detected in the germanite glasses. Probabilities of relaxation from ¹D₂ → ¹G₄ levels of Tm³⁺ in various glass hosts are calculated.