Yellow emission from dysprosium-doped ZBLAN fiber laser

In this paper, we report the first (to the best of our knowledge) GaN laser diode, emitting at 445 nm, pumped dysprosium (Dy) doped ZBLAN fiber laser for yellow emission using a simple setup. In our yellow laser experiment, we have used a commercially available Dy-doped ZBLAN fiber, which is originally designed for mid-infrared lasers demonstration and not optimized for visible laser design, as a laser active medium. For yellow (∼576 nm) lasing, we have exploited the ⁴F_9/2 to ⁶H_13/2 laser transition of a Dy ion, which is a quasi four level system. The performance of the yellow laser system is investigated by using two different Dy-doped fiber lengths (0.6 m and 5.95 m). The measured lasing thresholds are 7 mW and 28 mW for 0.6 m and 5.95 m of Dy-doped fiber, respectively. However, the maximum laser slope efficiency with respect to absorbed pump power is only 2.3% for 0.6 m of Dy-doped fiber. The laser slope efficiency decreases to 0.9% and the threshold increases to 28 mW for 5.95 m of Dy-doped fiber, which are result of fiber background loss at the signal wavelength. In addition, we have observed the pump excited state absorption at 445 nm pumping wavelength and estimated the pump ESA cross-section via numerical simulation.