A decade of mid-infrared, 3.5 <i>µ</i>m dual-wavelength pumped fiber lasers, review and perspective

It has been a decade since dual-wavelength pumping revolutionized the efficiency and power of the 3.5 µm transition in erbium-doped fluoride fibers, demonstrating the potential for near-watt level output from fiber lasers operating well beyond 3 µm. Since then, the dual-wavelength pumping technique has driven considerable advances and a deeper understanding of this transition. In this contribution, we summarize the progress in this field and outline the steps necessary for further significant advancements.