Anharmonic overtones quenching in Er3+ complexes

The organic complexes of the erbium ion Er3+ emitting in the near-infrared at 1.5 μm are widely investigated as potential active materials for a new generation of low-cost optical amplifiers for telecommunications. The limiting factor in these systems is the very low quantum yield of the lanthanide ion, generally ascribed to the presence of nearby high-energy vibrational centers as OH and CH bonds which are present as residual coordination water and as functional groups of the organic ligands. To make a quantitative prediction of the extent of the non-radiative decay originating from Förster transfer, the transition moments of the vibrational overtones in resonance with the ion emission have been evaluated from first principle calculations to compute the intensity of the fundamental normal modes; the overtone transitions intensities with energy falling in the 1.5 μm region have been evaluated by recursive analytical expressions obtained by using the Morse oscillator approximation.