Time-resolved switching characteristic of the nonlinear directionalcoupler under consideration of susceptibility dispersion

Two new forms of nonlinear coupled mode theory are presented which allow a quantitatively correct calculation of the temporal and spatial field evolution in a nonlinear coupler. The resultant set of coupled equations for the Fourier transforms of the pulse envelopes of the basis functions are numerically solved for representative coupling and excitation conditions. The approach permits the treatment of the power and time dependent switching characteristics of ultrashort pulses by accounting for the frequency dependence of the susceptibilities and coupling integrals. The results show that switching efficiency is low in the positive dispersion region due to pulse breakup. The pulse breakup can also be observed in the negative dispersion region, with pulses representing higher order solitons having a peak power on the order of the continuous-wave switching power