PT-symmetric coupler with a coupling defect: soliton interaction with exceptional point

TL;DR

This paper investigates how solitons interact with a local defect in a PT-symmetric coupler that can reach an exceptional point, revealing complex dynamics including breather formation, beam splitting, and blow-up phenomena.

Contribution

It introduces the study of soliton interactions with a coupling defect at the exceptional point in PT-symmetric systems, highlighting new dynamic behaviors and robustness of effects.

Findings

Symmetric solitons transform into breathers or blow up after defect interaction.

Anti-symmetric solitons exhibit broadening, splitting, breather formation, or blow-up.

Strong coupling leads predominantly to breather generation.

Abstract

We study interaction of a soliton in a parity-time (PT) symmetric coupler which has local perturbation of the coupling constant. Such a defect does not change the PT-symmetry of the system, but locally can achieve the exceptional point. We found that the symmetric solitons after interaction with the defect either transform into breathers or blow up. The dynamics of anti-symmetric solitons is more complex, showing domains of successive broadening of the beam and of the beam splitting in two outwards propagating solitons, in addition to the single breather generation and blow up. All the effects are preserved when the coupling strength in the center of the defect deviates from the exceptional point. If the coupling is strong enough the only observable outcome of the soliton-defect interaction is the generation of the breather.