Power scaling limits of thulium and thulium:holmium in the 2 µm spectral region: a comparison

The demand for high-power lasers in the 2 μm region is growing across various applications. Thulium-Doped Fiber Lasers (TDFL) lead with 50-60 % slope efficiencies and over 1 kW of output power. Thulium:Holmium-co-Doped Fiber Lasers (THDFL) show lower slope efficiencies but operate beyond 2.1 μm, beneficial for atmospheric applications. The latter laser type being so-far less explored. We compare TDFL and THDFL power scaling in a Master-Oscillator Power-Amplifier (MOPA) setup, assessing thermal constraints and output power limits for distinct fiber geometries. This study provides a direct comparison and important background on laser design to meet specific power requirements.