Numerical modeling of mid-infrared ultrashort pulse propagation in Er3+: fluoride fiber amplifiers

We present a numerical model to study the amplification and spectral conversion of ultrashort pulses at 2.8 μm in Er3+: fluoride fibers. This model includes accurate measurements of the gain and Raman properties of fluorozirconate fibers and agrees well with the experimental results. Interesting new features of such mid-infrared fiber amplifiers are discussed for various seeding conditions and fiber parameters. Among these features is the attractor property of the amplifier, which significantly increases the output stability of the tunable ultrafast system. When using the appropriate seed and fiber parameters, the model predicts the generation of a mid-infrared supercontinuum output with more than 4 W of average power or the generation of tunable ultrashort pulses above 3 μm with peak powers exceeding 400 kW.