Kilowatt-level, narrow linewidth, polarization-maintained all-fiber amplifiers based on multi-phase coded signal modulation and laser gain competition

Abstract In this paper, multi-phase coded signal (MPCS) modulation is demonstrated on high power narrow-linewidth polarization-maintained all-fiber amplifier for the first time. This technique is shown for stimulated Brillouin scattering (SBS) effect management and leads to as high as 737 W SBS threshold with FWHM linewidth of 4.6 GHz in single-tone 1064 nm polarization-maintained 20/400 μm fiber amplifier system. Further, in conjunction with laser gain competition where another signal laser operating at 1045 nm is applied, the 1064 nm output power could increase to 1023 W, at which the polarization extinction ratio (PER) is 13.3 dB and the output beam quality is measured to be Mx2/My2=1.29/1.28. This power scaling result provides a feasible method for linewidth controlling in high power fiber amplifier, which represents significance for high-power coherently and spectrally beam combining system.