Kerr beam self-cleaning on the $LP_{11}$ mode in graded-index multimode fiber

TL;DR

This paper demonstrates Kerr beam self-cleaning in graded-index multimode fibers, where nonlinear effects reshape the output beam into specific modes, notably the $LP_{11}$ mode, under certain conditions.

Contribution

It reports the first experimental observation of Kerr self-cleaning into the $LP_{11}$ mode in graded-index multimode fibers, expanding understanding of nonlinear mode dynamics.

Findings

Self-cleaning into the $LP_{11}$ mode observed at higher power thresholds.

Nonlinear mode coupling reshapes speckle patterns into low-order modes.

Threshold for $LP_{11}$ mode self-cleaning is about three times higher than for $LP_{01}$.

Abstract

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 $LP_{01}$ mode. For specific coupling conditions, nonlinear coupling among the guided modes can reshape the output speckle pattern generated by a pulsed beam into the low order $LP_{11}$ mode. This 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 $LP_{11}$ mode self-cleaning was about three times larger than that required for Kerr nonlinear self- cleaning into the $LP_{01}$ mode.