Dynamics of higher-order solitons in regular and PT-symmetric nonlinear couplers

TL;DR

This paper investigates the behavior, stability, and dynamics of higher-order solitons in both regular and PT-symmetric nonlinear couplers, revealing larger stability regions for antisymmetric solitons and identifying regimes of soliton splitting and resonance effects.

Contribution

It provides the first detailed analysis of higher-order soliton dynamics and stability in PT-symmetric couplers, including the discovery of larger stability regions for antisymmetric solitons.

Findings

Antisymmetric 2-solitons have larger stability regions than symmetric ones.

Identified stability borders against blowup in PT-symmetric systems.

Discovered resonance-induced splitting of 2-solitons into pairs of solitons.

Abstract

Dynamics of symmetric and antisymmetric 2-solitons and 3-solitons is studied in the model of the nonlinear dual-core coupler and its PT-symmetric version. Regions of the convergence of the injected perturbed symmetric and antisymmetric N-solitons into symmetric and asymmetric quasi-solitons are found. In the PT-symmetric system, with the balanced gain and loss acting in the two cores, borders of the stability against the blowup are identified. Notably, in all the cases the stability regions are larger for antisymmetric 2-soliton inputs than for their symmetric counterparts, on the contrary to previously known results for fundamental solitons (N=1). Dynamical regimes (switching) are also studied for the 2-soliton injected into a single core of the coupler. In particular, a region of splitting of the input into a pair of symmetric solitons is found, which is explained as a manifestation of the resonance between the vibrations of the 2-soliton and oscillations of energy between the two cores in the coupler.