Stimulated Brillouin Scattering Enhancement Factor Improvement in a 11.6-GHz-Linewidth 1.5-kW Yb-Doped Fiber Amplifier**Supported by the National Natural Science Foundation of China under Grant Nos U1330134, 61308024 and 11174305, the National High-Technology Research and Development Program of China under Grant No 2014AA041901, and the Shanghai Natural Science Foundation under Grant No 11ZR1441400.

Abstract

The stimulated Brillouin scattering (SBS) threshold enhancement factor in a pure white noise linewidth broadening Yb-doped fiber amplifier (YDFA) with a short large mode area fiber is theoretically and experimentally studied. We demonstrate a 1064.08 nm, 11.6 GHz linewidth, 1.5 kW output power YDFA with an SBS threshold enhancement of ~57 (26 W SBS threshold with single frequency seed). The output beam is near-diffraction limited with a beam quality factor of M2 = 1.15 and a slope efficiency of up to 87%. No SBS or stimulated Raman scattering effects are observed in the whole power range. Further power scaling is limited by the available pump power in our system.