Abstract

We investigated quatitatively the effect of two photon absorption (TPA) on soliton switching in a nonlinear directional coupler. We found that TPA decreased the switching efficiency and increased the input peak power required to achieve the all-optical switching. In addition, the output pulse width is broadened. A set of two linearly coupled nonlinear Schrodinger equations, describing soliton switching, were numerically solved by using the beam propagation method. We considered a linear coupling constant of 0.25 for a half-beat length coupler that had unity cw switching power. At low input power, the output occurred at the cross mode. As the input pulse power increased, the output switched to the bar mode. A maximum of 96% of the output energy appeared in the bar mode when the input peak power was about 1.55 (normalized to the cw switching power) and TPA = 0. When TPA was nonzero, the maximum fraction of the output energy in the bar mode decreased. For example, for TPA = 0.1, the maximum fraction was about 83%, while for TPA = 0.2 it was about 66%. Also, the input peak power required to achieve the maximum fraction output in the bar mode increased. For example, for TPA = 0.1 it was about 1.95, while for TPA = 0.2 it was about 2.4.

© 1992 Optical Society of America