Abstract

Due to enhanced absorption at 976nm Er³⁺:Yb³⁺ co-doped fused silica fibres are the common choice for high power fibre amplifiers at 1.5μm and optimizing the efficiency of the Yb³⁺ to Er³⁺ energy transfer is a main concern. However, not only the energy transfer may restrict the achievable efficiencies, as clustering and up-conversion effects of the Er³⁺ ions can also have a negative impact. Typically, the up-conversion is simply modelled in the rate equations as a term proportional to the squared population inversion. However, results from Monte-Carlo simulations [1] and from a more sophisticated stochastic model (including energy migration) [2] imply that this simple model is not necessarily suitable in general. The detrimental effect of clustering can be best described within the PIQ&HUC model [3]. Within this model, some of the ions are confined to pairs in which only one of the ions can be inverted due to strong up-conversion processes (pair induced quenching) and rest of the ions can interact independently with each other via up-conversion (homogeneous up-conversion). It was found that the stochastic model is more suitable to describe experimental data for an Er³⁺-doped phosphate fibre than the PIQ&HUC model [2]. However, no such analysis has been performed so far for Er³⁺-doped or Er³⁺:Yb³⁺ co-doped fused silica fibres, yet.

© 2015 IEEE