Experimental study of SBS suppression and coherence property of 1064 nm high power multi-tone fiber amplifier

Seeding high power fiber amplifier employing multi-tone fiber laser is an effective approach to suppress stimulated Brillouin scattering (SBS). In this paper, a two-stage 1064 nm high power fiber amplification system was set up. Single-, two- and three-tone fiber lasers were employed. SBS threshold powers and maximum output powers of the multi-tone cases are enhanced compared with the single-tone case. The multi-tone amplifiers also show comparable optical-to-optical efficiency to the single-tone amplifier. To demonstrate and validate coherence property of the two multi-tone fiber amplifiers, the output laser beams of the amplifiers were self-interfered in our self-made coherent beam combining system. The laser beams of the multi-tone cases showed good coherence property comparable to the single-tone case, which implied that the high power output laser light of the multi-tone fiber amplifiers could be used for coherent beam combining.

► SBS and coherence property of the multi-tone amplifiers are studied experimentally.
► The SBS thresholds of the multi-tone cases are higher than the single-tone case.
► The maximum outputs of the multi-tone cases are enhanced too.
► All the amplifiers have nearly the same optical-to-optical efficiency.
► The high power laser of the multi-tone amplifiers is fit for coherent beam combining.