Dynamics of high-power erbium–ytterbium fiber amplifiers

Dynamic regimes of high-peak-power erbium–ytterbium (Er3+–Yb3+) codoped fiber amplifiers are analyzed for nanosecond-to-microsecond pulses. High-energy pulse generation requires a large-core fiber amplifier to increase energy storage and the threshold of nonlinear effects. A numerical model of large-core Er3+–Yb3+ fiber amplifiers is described. Dynamics of peak powers, amplified spontaneous emission, and population inversion are presented. Influence of radial dependence and reflections at the extremities are studied. Modeling and experimental results are compared for simple-pass and double-pass amplifier configurations. The role of parasitic reflections is highlighted. A semianalytical model is derived for low and high repetition rates.