Optimisation of cascaded Yb fiber amplifier chains using numerical-modelling

We show that it is possible to adapt existing software packages developed originally for modeling telecommunication devices and systems to reliably predict and optimize the performance of high-power Ytterbium-doped fiber amplifier and laser systems. The ready availability of a flexible, user-friendly design tool should be of considerable practical interest to scientists and engineers working with this important new laser technology since Ytterbium amplifier and amplifier cascades are often difficult to optimize experimentally due to the three-level nature of the Ytterbium laser transition. As examples of the utility and accuracy of the software, as well as the complexity of the systems and amplifier properties that can be successfully modeled, we present a comparison of experimental and theoretical results for individual core and cladding pumped amplifiers, and also for an ultra-short pulse four-stage amplifier system optimized both to provide a broad gain bandwidth and to minimize nonlinear effects. We also show how high energy 100 ns pulses with complex user definable temporal profiles can be created in a gain-saturated amplifier by suitable pre-shaping of the low-energy input pulses. Furthermore, with appropriate modifications the same software package can be applied to fiber amplifiers based on other rare-earth elements and glass hosts. (C) 2006 Optical Society of America.