Ultrabroadband Dispersive Radiation by Spatiotemporal Oscillation of Multimode Waves

Abstract

In nonlinear dynamical systems, qualitatively distinct phenomena occur depending continuously on the size of the bounded domain containing the system. For nonlinear waves, a multimode waveguide is a bounded three-dimensional domain, allowing observation of dynamics impossible in open settings. Here we study radiation emitted by bounded nonlinear waves: the spatiotemporal oscillations of solitons in multimode fiber generate multimode dispersive waves over an ultrabroadband spectral range. This work suggests routes to sources of coherent electromagnetic waves with unprecedented spectral range.

Spatial beam self-cleaning in multimode fibres

“…Reference [21] proposed to use this effect for combining multiple laser beams into a single one. Recent experiments reported supercontinuum generation (SCG) of femtosecond light pulses in the anomalous dispersion regime of graded-index (GRIN) MMFs: the close resemblance with self-focusing and multiple filamentation suggested the potential role of GRIN MMFs for achieving beam cleanup through control of the input launching conditions [3,4].In this Letter, we experimentally demonstrate that a single strong laser beam can display enhanced brightness when propagating through MMFs. We show a new regime of remarkably stable self-induced bellshaped beam propagation in MMFs based on the nonlinear nonreciprocity of mode coupling that occurs in the normal dispersion regime.…”

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Multimode optical fibres are enjoying a renewed attention, boosted by the urgent need to overcome the current capacity crunch of single-mode fibre systems and by recent advances in multimode complex nonlinear optics [1][2][3][4][5][6][7][8][9][10][11][12][13]. In this work, we demonstrate that standard multimode fibres can be used as ultrafast all-optical tool for transverse beam manipulation of high power laser pulses.

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“…In fibres with parabolic index profile, the propagation constants of the modes take equally spaced values, so that coherent mode beating induces a periodic local intensity oscillation along the fibre, which the Kerr effect translates into a periodic longitudinal modulation of the refractive index [4,10,12]. With a simpler two-mode excitation, such type of self-induced or dynamic long-period Bragg grating was previously exploited in [25] for demonstrating light-controlled mode conversion in a GRIN MMF.…”

“…MMFs could provide a solution to meet increasing demands of new breakthrough technologies for light control and manipulation in communications, high-power fibre lasers and metrology [1,2,16]. In fundamental physics, MMFs may provide a natural tool for investigating spatiotemporal soliton dynamics [5,6], and for unveiling new, exciting nonlinear phenomena [3,4,9,13].…”

“…Reference [21] proposed to use this effect for combining multiple laser beams into a single one. Recent experiments reported supercontinuum generation (SCG) of femtosecond light pulses in the anomalous dispersion regime of graded-index (GRIN) MMFs: the close resemblance with self-focusing and multiple filamentation suggested the potential role of GRIN MMFs for achieving beam cleanup through control of the input launching conditions [3,4].…”