Numerical modeling and optimization of hundred-watt-level 2.8 μm and 1.6 μm cascaded heavily-erbium-doped fluoride fiber amplifiers

We propose a continuous-wave dual-seed cascaded heavily erbium-doped fluoride fiber amplifier scheme with a 981 nm bi-directional pump configuration for hundred-watt-level power scaling for the first time. When the powers of the 2.8 mu m and 1.6 mu m seed lasers and the total pump light are 5 W, 20 W, and 300 W, respectively, the 2.8 mu m laser theoretically achieves an output power of similar to 100 W. The amplifier scheme can also reduce the fiber temperature. Additionally, the results show that there is no excited state absorption at similar to 1.675 mu m, and thus injecting a 1.675 mu m laser to the amplifier is not conducive to the power scaling.