Stable dark solitons in PT-symmetric dual-core waveguides

TL;DR

This paper constructs and analyzes the stability of dark solitons in a PT-symmetric nonlinear dual-core waveguide model, combining analytical and numerical methods to identify stable regimes and collision dynamics.

Contribution

It introduces a novel PT-symmetric dual-core waveguide model with stable dark solitons and thoroughly investigates their stability and interactions.

Findings

Stable dark solitons are identified in the model.

Stability regions are mapped in parameter space.

Numerical simulations confirm analytical stability predictions.

Abstract

We construct dark solitons in the recently introduced model of the nonlinear dual-core coupler with the mutually balanced gain and loss applied to the two cores, which is a realization of parity-time symmetry in nonlinear optics. The main issue is stability of the dark solitons. The modulational stability of the CW (continuous-wave) background, which supports the dark solitons, is studied analytically, and the full stability is investigated in a numerical form, via computation of eigenvalues for modes of small perturbations. Stability regions are thus identified in the parameter space of the system, and verified in direct simulations. Collisions between stable dark solitons are briefly considered too.