SBS suppression through seeding with narrow-linewidth and broadband signals: experimental results

We present experimental verification of a novel technique to suppress stimulated Brillouin scattering (SBS) in single frequency fiber amplifiers. This technique relies on seeding with a combination of broadband and single frequency laser beams to allow for efficient laser gain competition between the two signals. In the experiment, a monolithic fiber configuration was used. Broadband 1045 nm light and single frequency 1064 nm light were coupled into an Yb-doped gain fiber. With appropriate selection of seed power ratio, we were able to generate an output signal predominantly comprised of 1064 nm light while simultaneously suppressing the back-scattered Stokes light. The slope efficiency for the two-tone amplifier was approximately 78%; slightly below that of a single-tone amplifier. The SBS threshold for the former, on the other hand, was appreciably higher than that of the latter which is in excellent agreement with the theory. In preliminary implementation of this technique at high power, we generated close to 100 W without encountering the SBS threshold. Finally, we show numerically that due to a favorable thermal gradient much higher powers can be obtained.