Numerical analysis of beam self-cleaning in multimode fiber amplifiers

Recent experimental results have reported the observation of beam self-cleaning or, more generally, nonlinear reshaping in active multimode fibers. In this work, we present a numerical analysis these processes by considering ideal case diode-pumped signal amplifier made graded-index fiber with uniform Yb doping. Simulations confirm that cleaning may take place even amplifying fibers, absence power conservation. Moreover, show how local intensity maxima, which are periodically generated self-imaging process, influence population inversion doping atoms, and locally saturate gain.