Soliton states in a nonlinear directional coupler with intermodal dispersion

We study numerically the propagation of short optical pulses in a nonlinear directional coupler that possesses significant intermodal dispersion. Using the split-step method with fast Fourier transform, we calculate the soliton solutions of such a coupler and highlight the effect of intermodal dispersion on the propagation dynamics of the pulses. We find that the intermodal dispersion has only a small effect on the shape of the soliton states, in spite of the fact that it can distort and break up low-energy pulses launched into one arm of the coupler. The intermodal dispersion, however, can cause a drift in the velocity of the soliton pulses.