Nonlinear switching and reshaping of slow-light pulses in Bragg-grating couplers

We study the propagation and switching of slow-light pulses in nonlinear directional couplers composed of two parallel waveguides, where each waveguide contains a Bragg grating. We show that by optimizing the phase shift between the Bragg gratings, one can obtain specific dispersion characteristics enabling all-optical pulse manipulation in space and in time. We demonstrate that the power-controlled nonlinear self-action of light can be used to compensate dispersion-induced broadening of pulses through the formation of gap solitons, to control pulse switching in the coupler, and to tune the propagation velocity. We also confirm that the switching is tolerant to deviations of the phase shift from the optimal value, which can occur in the fabrication process.