Nonlinear beam self-imaging and self-focusing dynamics in a GRIN multimode optical fiber: theory and experiments
Abstract
Beam self-imaging in nonlinear graded-index multimode optical fibers is of interest for many applications, such as implementing a fast saturable absorber mechanism in fiber lasers via multimode interference. We obtain an exact solution for the nonlinear evolution of first and second order moments of a laser beam carried by a graded-index multimode fiber, predicting that the spatial self-imaging period does not vary with power. Whereas the amplitude of the oscillation of the beam width is power-dependent. We have experimentally studied the longitudinal evolution of beam self-imaging by means of femtosecond laser pulse propagation in both the anomalous and the normal dispersion regime of a standard telecom graded-index multimode optical fiber. Light scattering out of the fiber core via visible fluorescence emission and harmonic wave generation permits us to directly confirm that the self-imaging period is invariant with power. Spatial shift and splitting of the self-imaging process under the action of self-focusing are also emphasized.
Keywords
Cite
@article{arxiv.2005.07280,
title = {Nonlinear beam self-imaging and self-focusing dynamics in a GRIN multimode optical fiber: theory and experiments},
author = {Tobias Hansson and Alessandro Tonello and Tigran Mansuryan and Fabio Mangini and Mario Zitelli and Mario Ferraro and Alioune Niang and Rocco Crescenzi and Stefan Wabnitz and Vincent Couderc},
journal= {arXiv preprint arXiv:2005.07280},
year = {2020}
}