Soliton–soliton interactions in a grating-assisted coupler with cubic-quintic nonlinearity

Abstract

We systematically investigate the interaction of co-propagating Bragg grating solitons in a dual-core fibre in which one of the cores has a Bragg grating written a cubic-quintic nonlinear medium and the other one is linear and uniform. In a previous work, it has been shown that this structure supports two disjoint families of Bragg grating solitons (called Type 1 and Type 2). Type 1 solitons can be viewed as the generalization of Bragg grating solitons in the semilinear coupled system with cubic nonlinearity. On the other hand, Type 2 solitons exist where quintic nonlinearity is more pronounced. It has also been shown that Type 2 solitons are always unstable. However, Type 1 solitons can be stable in a portion of the bandgap. Interactions between stable in-phase Type 1 quiescent solitons may result in the destruction of one or both solitons, symmetric or asymmetric separation, merger into a quiescent soliton and 2→3 transformation. The effects of the coupling coefficient, group velocity mismatch, initial phase difference and the separation between the solitons on the outcome of interactions are analysed.