Dynamics of colliding counterpropagating solitons in coupled Bragg gratings with cubic-quintic nonlinearity

Abstract

ABSTRACTThe collisions of moving gap solitons in a system of two linearly coupled identical Bragg gratings with cubic-quintic nonlinearity are investigated systematically. In a previous work, it was found that the model supports two disjoint families of solitons, referred to as Type 1 and Type 2 moving gap solitons. It was also shown that within each of these categories there exist both symmetric and asymmetric moving gap soliton solutions. The collisions of the π-out-of-phase Type 1 asymmetric solitons generally leads to the mutual repulsion of both solitons. However, in the case of π-out-of-phase Type 2 asymmetric solitons, the low velocity solitons repel each other, but the collision of high velocity ones results in the destruction of both solitons. Collisions of the in-phase Type 1 asymmetric moving gap solitons exhibit rich dynamics and a range of outcomes, such as the separation of solitons with identical, reduced, increased, asymmetric velocities, destruction of both solitons, and formation of a quiescent soliton, either through a merger or through transformation. We have identified the outcome regions in the plane of quintic nonlinearity vs. frequency for different coupling coefficients and velocities. The interplay between the coupling coefficient and the velocity on the outcome regions is investigated. Also, the effect of the initial phase difference on the formation of quiescent solitons and the transformation is analysed.