Abstract
We investigate the existence, stability, and collision dynamics of moving gap solitons in a model of two linearly coupled Bragg gratings with dispersive reflectivity. It is shown that the model supports both symmetric and asymmetric moving solitons that fill the entire bandgap. It is found that beyond a certain value of the dispersive reflectivity parameter, the moving solitons develop sidelobes. To analyze the sidelobes, exact analytical expressions for the tails of the symmetric solitons are found and it is shown that they are in excellent agreement with the numerical solutions. By means of numerical stability analysis, we have identified stability regions within the bandgap for various values of dispersive reflectivity, coupling coefficient, and velocity. It is found that dispersive reflectivity has a stabilizing effect. We have also systematically investigated the collisions of in-phase and -out-of-phase counterpropagating solitons. In-phase collisions lead to various outcomes such as separation of solitons with reduced, increased, or unchanged velocities; merger into a single quiescent soliton; and generation of three solitons (one quiescent and two moving solitons). A key finding is that depending on the velocity and coupling coefficient, collisions may lead to the formation of three solitons even in the absence of dispersive reflectivity. In the out-of-phase case, it is found that colliding solitons generally bounce off each other.
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