Signal coupling in nonlinear hybrid optical structures: A numerical approach

The numerical study of intensity-dependent picosecond solitonic pulse coupling in nonlinear fiber grating couplers, configured with in-phase or out-of-phase uniform Bragg gratings, is reported in the present work. The time domain non-linear coupled-mode equations that model the coupling dynamics in the devices under investigation are solved numerically by the choice of a fourth-order modified predictor-corrector method. The switching performance of the devices have been investigated as a function of the input power. Characteristically, the coupling effect is dependent on the operational power level, geometry, and, in particular, the mismatching between the adjacent gratings. In the linear regime, the numerical results indicate that the relative shift of the gratings can strongly modify the reflectivity of the optical modes, impacting on the extraction efficiency. As the intensity of the input pulses increases, the hybrid character of the devices vanishes, being the coupling results very similar, independently of the proposed arrangement.