Demonstration of 50-W-level all-fiber oscillator operating near 980 nm with the 20-μm core-diameter double-cladding Yb-doped fiber

Abstract

In this paper, a cost-effective 50-W-level all-fiber oscillator operating near 980 nm is demonstrated with the 20-μm core-diameter double-cladding Yb-doped fiber (DCYF) firstly, to the best of our knowledge. By using the 15-degree angle-cleaved output fiber end-facet, the record 54.8-W output power is obtained with the slope efficiency about 15.6%. It is revealed that increasing the cleaved angle (or suppressing the optical feedback) of output fiber end-facet should be an effective way to improve the performance of the fiber oscillator. Then, by optimizing the length of DCYF, the slope efficiency is slightly improved to 15.8% because of better suppression of the amplified spontaneous emission (ASE) around 1030 nm. It is also found that the effect of pumping scheme is negligible on the performance of the fiber oscillator. The beam quality is measured and the M2 factor is about 2.5. Better beam quality can be expected by lowering the numerical aperture (NA) of the active fiber core. The all-fiber oscillator can provide a well solution for the high-power core-pump source.