Diffraction-limited operation from a multimode LMA fiber using active digital holography precompensation

The authors report on the active wavefront control of a multimode fiber (MMF) beam using the digital holography principle. Coherent combining of the spatial modes of a MMF seems an interesting alternative to separated emitters because of reduced relative thermal drifts, simpler and integrated architecture and the possibility to use standard MMF. The technique allows the use of very large mode area fiber amplifiers without the need of beam cleanup at the output, while retaining a good spatial beam quality.