Discrete vortex solitons and PT symmetry

TL;DR

This paper investigates how PT symmetric defects influence discrete vortex modes in nonlinear waveguide arrays, revealing new control mechanisms for vortex stability and symmetry breaking.

Contribution

It demonstrates the impact of PT symmetry on vortex mode degeneracy, stability, and the emergence of nonlinear modes with real propagation constants.

Findings

PT symmetry causes vortex mode degeneracy to break and eigenvalues to become complex.

Nonlinear modes with real propagation constants can still exist despite symmetry breaking.

Vortex stability depends on charge magnitude and sign, enabling new control methods.

Abstract

We study the effect of lifting the degeneracy of vortex modes with a PT symmetric defect, using discrete vortices in a circular array of nonlinear waveguides as an example. When the defect is introduced, the degenerate linear vortex modes spontaneously break PT symmetry and acquire complex eigenvalues, but nonlinear propagating modes with real propagation constants can still exist. The stability of nonlinear modes depends on both the magnitude and the sign of the vortex charge, thus PT symmetric systems offer new mechanisms to control discrete vortices.