KW narrow linewidth all fiber laser

Recently, high power narrow linewidth fiber lasers are interested in wavelength beam combining. In narrow linewidth fiber laser, Stimulated Brillouin Scattering is the main power limiting factor. A Stimulated Brillouin Scattering suppressing method by modulating frequency distribution was proposed and examined both experimentally and theoretically. The Stimulated Brillouin Scattering threshold power increased a lot by increasing the frequency number and spacing. Finally, the linewidth of 8 GHz, power of 1kW and central wavelength of 1064.14nm, are achieved respectively in fiber laser. We analyzed the above results: the increasing of frequency number, controlling of frequency spacing all reduce power spectrum density. With the cascaded phase modulation technology, the Stimulated Brillouin Scattering threshold is increased, while the output power of fiber laser is increased a lot.