Abstract

Solitons are well known solutions of the nonlinear Schrödinger equation (NLSE). In optics, temporal solitons are localized wavepackets that travel unperturbed in dispersive Kerr media. They can be of different order, with only first order solitons strictly maintain their shape as they propagate, while higher order solitons periodically oscillate along the waveguide. If the propagation deviates from purely Kerr and quadratically dispersive, higher order solitons tend to split into several lower order solitons. This process, often called soliton fission, is the main mechanism underlying supercontinuum generation [1]. In silica fibers, the fission is most often induced by the Raman effect and third-order dispersion. The recent push for optical integration has led to a number of demonstrations of supercontinuum generation in semiconductor nanowaveguides [2]. But with the focus on coherent spectral broadening for frequency comb applications, few studies discuss the reason for the decay of the input soliton. It was shown last year that free carriers can, by blue-shifting the soliton, induce fission in Indium Gallium Phosphide (InGaP) nanowaveguides [3]. Moreover it was suggested that free carrier dispersion drives soliton fission in our recent experiments of supercontinuum generation in silicon wire waveguides [3,4].

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