Beam cleanup in a self-aligned gradient-index Brillouin cavity for high-power multimode fiber amplifiers

Abstract

We propose a beam cleanup setup to convert a multimode beam into a single-mode beam by use of the Brillouin effect in a multimode gradient-index (GI) fiber. Phase conjugation and beam cleanup regimes in highly multimode fibers are discussed, and the self-aligned GI fiber Brillouin cavity is presented. We report a preliminary conversion from an M2=6.5 beam into an M2=1.3 beam with 31% efficiency.