Nonlinear beam self-imaging and self-focusing dynamics in a GRIN multimode optical fiber: theory and experiments
- Resource Type
- Working Paper
- Authors
- Hansson, Tobias; Tonello, Alessandro; Mansuryan, Tigran; Mangini, Fabio; Zitelli, Mario; Ferraro, Mario; Niang, Alioune; Crescenzi, Rocco; Wabnitz, Stefan; Couderc, Vincent
- Source
- Subject
- Physics - Optics
Nonlinear Sciences - Pattern Formation and Solitons
- Language
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.