All-fiber Tm:Ho-codoped fiber laser at 2160 nm

Efficient laser emission at long wavelengths (2.1–2.2 µm) is interesting for applications like nonlinear frequency conversion and atmospheric measurements. While Tm³⁺-doped fibers can be efficiently pumped at 793 nm, their low cross-sections limit laser emission, while Ho³⁺-doped systems are often preferred, they rely on Tm³⁺-doped fiber lasers for long-wavelength pumping, adding complexity. B. Anderson et al. have demonstrated up to 2.13 µm with 87 W of output power using a Tm³⁺-doped fiber. Tm³⁺:Ho³⁺-codoped fibers offer a promising alternative, enabling efficient 793 nm pumping for long-wavelength emission. Power output of 145 W at 2.2 µm has been demonstrated by P. Forster. However, free-space setups can face thermal misalignment issues. Thus, this contribution presents a first investigation of an all-fiber laser system at 2.16 µm.