Optical spectroscopy and local structure of Er3+ luminescence centres in СaO–Ga2O3–GeO2 glasses

Optical absorption, luminescence excitation and emission spectra of Er 3+ centres in Ca 3 Ga 2 Ge 3 O 12 :Er glass with Er content of 1.46wt% are presented and analysed. Luminescence kinetics for the main Er 3+ transitions was satisfactorily described by single exponential decays with characteristic lifetimes. Oscillator strengths, phenomenological Judd-Ofelt intensity parameters, radiative decay rates (emission probabilities of transitions), branching ratios and radiative lifetimes for Er 3+ centres in Ca 3 Ga 2 -Ge 3 O 12 :Er glass are calculated and compared with the corresponding parameters of the Ca 3 Sc 2 Ge 3 O 12 :Er 3+ garnet and other crystals and glasses. Quantum efficiency, n, of the 4 I 13/2 → 4 I 15/2 Er 3* transition is determined. Incorporation peculiarities and local structure of Er 3+ luminescence centres in Ca 3 Ga 2 Ge 3 O 12 :Er + glass are discussed in comparison with garnet crystals and oxide glasses. On the basis of the presented results and referenced EXAFS data for Er, Eu and Ho impurities (L 3 -edge) it has been shown that Er 3* centres in Ca 3 Ga 2 Ge 3 O 12 glass occupy network sites with the coordination number to oxygen of N=6.