Abstract

Diode-pumped erbium-doped fluoride glass (Er:FG) fiber lasers operating near the water absorption peak have a potential use in medical [1] and spectroscopy [2] applications. However, their efficiency is generally limited to the maximum Stokes efficiency limit of ~35%. Until now, the only way demonstrated to exceed this limit takes advantage of an energy transfer upconversion process (ETU). Nonetheless, such ETU processes are only efficient in heavily doped fibers which lead to high heat load per unit length of the fiber, thus limiting the power scaling potential of such an approach. To date, the highest slope efficiency of 35.4%, slightly exceeding the Stokes limit, was reported through ETU with a 7 mol. % Er³⁺:FG fiber laser emitting near 2.8 µm [3].

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