Quartic-dispersion-induced modulational instability in coupled nonlinear Chen–Lee–Liu systems

Lucien Mandeng Mandeng, Dieudonné Zanga and Roger Bertin Djob

Chaos, Solitons & Fractals, 2026, vol. 202, issue P1

Abstract: We investigate modulational instability (MI) in coupled nonlinear optical waveguides governed by the extended coupled Chen–Lee–Liu equations (CLLEs), incorporating both second-order and fourth-order chromatic dispersions as well as Kerr and coupled Chen–Lee–Liu (CLL) nonlinearities. The interplay between group-velocity dispersion (GVD) and fourth-order dispersion (FOD) is shown to critically determine the MI gain spectrum. Opposite-sign GVD-FOD combinations (β2jβ4j<0) maximize the spectral bandwidth and generate multiple gain lobes, while same-sign configurations suppress them. Numerical simulations using stationary and Akhmediev-breather-type inputs confirm that MI drives solitonic fission and the emergence of pure-quartic soliton (PQS) trains, particularly under normal FOD with balanced nonlinear coefficients. Imbalances in cross-CLL or Kerr terms modify the spectral structure, affecting lobe separation and MI strength. Optimal MI arises from normal FOD combined with balanced nonlinearities and moderate input power. These findings provide a comprehensive framework for tailoring MI gain spectra, controlling spectral lobe dynamics, and engineering efficient PQS generation, offering new insights for dispersion-managed waveguides, supercontinuum generation, and ultrafast pulse shaping in nonlinear photonic systems.

Keywords: Modulational instability; Chen–Lee–Liu Equation; Linear analysis; Quartic dispersion; Group-velocity dispersion; Nonlinearities (search for similar items in EconPapers)
Date: 2026
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Persistent link: https://EconPapers.repec.org/RePEc:eee:chsofr:v:202:y:2026:i:p1:s0960077925015474

DOI: 10.1016/j.chaos.2025.117534

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