Active coherent superposition of five fiber amplifiers at 670W using multiplexed volume Bragg gratings

We present an experimental study on active coherent combining of five Yb (Ytterbium)-doped fiber laser amplifiers that employs multiplexed volume Bragg gratings (MVBGs), reporting a combining efficiency of 82% and near-diffraction limited beam quality at a combined input power of 380 W, and 70% combining efficiency with equal beam quality at 670 W input power.