Suppressing nonlinear effects in multimode fiber amplifiers with high beam quality

Stimulated Brillouin Scattering (SBS) is a major issue for delivering intense radiation through a fiber and for high-power fiber laser amplifiers. While most SBS-suppression techniques strive to maintain single-mode operation for high beam quality, we experimentally and theoretically demonstrate that coherent excitation of many fiber modes can significantly increase the SBS threshold while maintaining good output-beam quality. By shaping the wavefront of a coherent seed with a spatial light modulator, many fiber modes are excited and the output is focused to a single diffraction-limited spot.