Single mode 43 kW output power from a diode-pumped Yb-doped fiber amplifier

TLDR

The study investigates scaling two diode‑pumped Yb‑doped fiber amplifiers to produce diffraction‑limited beams. Spectral broadening was employed to suppress stimulated Brillouin scattering, allowing output power to reach 4.3 kW limited only by pump power. The amplifiers achieved up to 4.3 kW average output with 90 % slope efficiency, diffraction‑limited beam quality, no transverse mode instability or stimulated Raman scattering, and a spectral dynamic range exceeding –80 dB.

Abstract

We investigate the average power scaling of two diode-pumped Yb-doped fiber amplifiers emitting a diffraction-limited beam. The first fiber under investigation with a core diameter of 30 µm was able to amplify a 10 W narrow linewidth seed laser up to 2.8 kW average output power before the onset of transverse mode instabilities (TMI). A further power scaling was achieved using a second fiber with a smaller core size (23µm), which allowed for a narrow linewidth output power of 3.5 kW limited by stimulated Brillouin scattering (SBS). We mitigated SBS using a spectral broadening mechanism, which allowed us to further increase the output power to 4.3 kW only limited by the available pump power. Up to this power level, a high slope efficiency of 90% with diffraction-limited beam quality and without any sign of TMI or stimulated Raman scattering for a spectral dynamic range of higher than -80 dB was obtained.