Kerr beam self-cleaning on the LP11 mode in graded-index multimode fibers

We report the experimental observation of Kerr beam self-cleaning in a graded-index multimode fiber, leading to output beam profiles different from a bell shape, close to the LP01 mode. For specific light injection conditions, nonlinear coupling among the guided modes can reshape the output speckle pattern generated by a pulsed beam into the low order LP11 mode. This effect was observed in a few meters-long multimode fiber with 750 ps pulses at 1064 nm in the normal dispersion regime. The power threshold for LP11 mode self-cleaning was about three times larger than that required for Kerr nonlinear self-cleaning into the LP01 mode. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement