Two-component solitons under a spatially modulated linear coupling: Inverted photonic crystals and fused couplers

TL;DR

This paper investigates two-component solitons and their symmetry-breaking behaviors in spatially modulated linear coupling systems, revealing power-dependent bifurcation types in photonic crystals and fused couplers.

Contribution

It introduces a novel analysis of symmetry-breaking bifurcations in systems with spatially varying linear coupling, including an exact analytical model for fused couplers.

Findings

Bifurcation type changes from sub- to supercritical with increased power.

Spatial modulation of coupling affects soliton symmetry-breaking.

Analytical solutions for bifurcation behavior in fused couplers.

Abstract

We study two-component solitons and their symmetry-breaking bifurcations (SBBs) in linearly coupled photonic systems with a spatially inhomogeneous strength of the coupling. One system models an inverted virtual photonic crystal, built by periodically doping the host medium with atoms implementing the electromagnetically induced transparency (EIT). In this system, two soliton-forming probe beams with different carrier frequencies are mutually coupled by the EIT-induced effective linear interconversion. The system is described by coupled nonlinear Schr\"{o}dinger (NLS) equations for the probes, with the linear-coupling constant periodically modulated in space according to the density distribution of the active atoms. The type of the SBB changes from sub- to supercritical with the increase of the total power of the probe beams, which does not occur in systems with constant linear-coupling constants. Qualitatively similar results for the SBB of two-component solitons are obtained, in an exact analytical form, in the model of a fused dual-core waveguide, with the linear coupling concentrated at a point.