Optimizing the mode instability threshold of high-power fiber laser systems

In this work we present guidelines to increase the transverse mode instability threshold of high power fiber amplifiers and also, for the first time to the best of our knowledge, of fiber oscillators. These guidelines do not involve changes in the composition of the active material (except for its doping concentration), but they can still lead to a significant increase of the transverse mode instability threshold. The dependence of this parameter on the active ion concentration, the core conformation, the pump configuration and the mirror reflectivities in a fiber oscillator will be studied and discussed.