High-power diode-pumped fiber laser operating at 3 μm.

A high-power diode-cladding-pumped Ho³⁺-doped fluoride glass fiber laser operating in cascade mode is demonstrated. The ⁵I₆→⁵I₇ and ⁵I₇→⁵I₈ laser transitions produced 0.77 W at a measured slope efficiency of 12.4% and 0.24 W at a measured slope efficiency of 5.2%, respectively. Using a long fiber length, which forced a large threshold for the ⁵I₇→⁵I₈ transition, a wavelength of 3.002 μm was measured at maximum output power, making this system the first watt-level fiber laser operating in the mid-IR.