Directly diode-pumped mid-infrared dysprosium fiber laser.

We report the demonstration of a Dy-doped ZBLAN fiber laser directly diode-pumped at 800 nm utilizing a codoping scheme with Tm 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 Dy 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.