Edge and bulk dissipative solitons in modulated PT-symmetric waveguide arrays

TL;DR

This paper investigates how modulated PT-symmetric waveguide arrays can support stable dissipative solitons at edges or center, with their formation controlled by array modulation and nonlinear effects.

Contribution

It introduces a novel approach to control the location of dissipative solitons in PT-symmetric waveguide arrays through spatial modulation and nonlinearity.

Findings

Stable dissipative solitons can form at edges or center of arrays.

Array modulation influences PT-symmetry breaking and soliton localization.

Solitons exhibit triangular shapes and broaden with increased gain-loss levels.

Abstract

We address dissipative soliton formation in modulated PT-symmetric continuous waveguide arrays composed from waveguides with amplifying and absorbing sections, whose density gradually increases (due to decreasing waveguide separation) either towards the center of the array or towards its edges. In such a structure the level of gain/loss at which PT-symmetry gets broken depends on the direction of increase of the waveguide density. Breakup of the PT-symmetry occurs when eigenvalues of modes localized in the region, where waveguide density is largest, collide and move into complex plane. In this regime of broken symmetry the inclusion of focusing Kerr-type nonlinearity of the material and weak two-photon absorption allows to arrest the growth of amplitude of amplified modes and may lead to the appearance of stable attractors either in the center or at the edge of the waveguide array, depending on the type of array modulation. Such solitons can be stable, they acquire specific triangular shapes and notably broaden with increase of gain-loss level. Our results illustrate how spatial array modulation that breaks PT-symmetry locally can be used to control specific location of dissipative solitons forming in the array.