Design and Numerical Modeling of Broadband Mid-IR Rare-Earth-Doped Chalcogenide Fiber Amplifiers

The design of broadband chalcogenide double-clad fiber amplifiers doped with praseodymium, dysprosium, or terbium ions is reported. A theoretical study of ultrashort pulse amplification in the 4-5 μm range with allowance for realistic fiber parameters: dispersion, nonlinearity, background loss (2 dB/m), and Se-H impurity loss (7 dB/m at 4.6 μm) is presented. It is shown that a gain of more than 15 dB can be achieved for dysprosium amplifiers and more than 25 dB for praseodymium and terbium ones. The energy of pulses with a repetition rate of 5 MHz can be increased from 10 pJ up to ~1 nJ for dysprosium fibers and up to several nanojoules for praseodymium and terbium fibers. Further amplification by increasing pump power may be limited by a low damage threshold.