Numerical demonstration of a multistage cascaded Raman soliton shift structure in mid-infrared region

We demonstrated a three-stage cascaded Raman soliton frequency shift structure in mid-infrared region (MIR) through numerical simulation. By cascading germania-core fiber, Er3+ ZBLAN fiber amplifier with an indium fluoride or (InF3) or TeO2-Bi2O3-ZnO-Na2O (TBZN) fiber, we achieved 2-4.75 μm and 2-5.5 μm tunable range respectively. When the same tunable range was achieved, both the energy and conversion efficiency of Raman solitons in the designed three stage cascaded structure were greatly improved, comparing with structure with single Raman shifter fiber. Our work could provide an effective way to improve the energy and conversion efficiency of Raman solitons in the commonly used single Raman frequency shift structure.