Directly diode-pumped mid-infrared dysprosium fiber laser

We report the demonstration of a Dy³⁺-doped ZBLAN fiber laser directly diode-pumped at 800 nm utilizing a codoping scheme with Tm³⁺ serving as the donor ion. In this initial demonstration, a modest output power of 12 mW is generated with a slope efficiency of 0.3% at an emission wavelength of 3.23 μm. Energy transfer dynamics are investigated through excited state lifetime analysis and comparison to resonant pumping of the Dy³⁺ upper state. The likely presence of an energy transfer upconversion process is identified, which has an undesirable effect on 3 μm class lasers but may be of significant benefit for future 4 μm systems.