Elimination of the Photodarkening Effect in an Yb-Doped Fiber Laser With Deuterium

This study reports the radical elimination of the photodarkening (PD)-effect in Yb-doped fiber through deuterium loading. With deuterium pre-loading, no PD-induced excess loss of the Yb-doped fiber was observed under 915-nm pumping conditions. Moreover, the existing loss induced by the PD effect was also eliminated via deuterium loading, and the excess loss declined to nearly 0 dB/m. The method was also validated in a KW-level fiber laser experimental setup. In the 20/400-μm deuterium pre-loaded Yb-doped fiber, an output laser power of 1630 W and beam quality factor (M
²
) of 1.69 were obtained. The two parameters remained stable during the entire continuous operation process of 40 min, and displayed very little power fluctuation of <;0.5%. The results of our experiments confirmed that deuterium loading can protect Yb-doped fibers from the PD effect, thereby improving the power and mode stability, which is often deteriorated by PD. Notably, the results of this study are beneficial in terms of further development of high-power fiber lasers.