Abstract

The nonlinear directional coupler has well-known optical switching properties. Unfortunately, since the characteristic coupling length depends on the instantaneous value of the power, ulstrashort pulses will break up in the coupler. However, if pulses are used which have pulse widths and peak powers comparable with those of solitons for the uncoupled guides, the pulses are essentially unperturbed by the switching process. We have numerically studied such soliton switching in a nonlinear directional coupler doped with erbium ions. We find that the presence of a small amount of gain (provided by the erbium) enhances the efficiency of the switching process. In addition, the switched pulses display the compression normally observed with adiabatically amplified solitons. Apart from this compression, little other distortion of the pulse shape occurs during propagation through the coupler. As a result, we have shown that it is possible to provide all-optical switching, amplification, and compression of short pulses in a single device. We have also considered the effects of gain dispersion on the switching. The main effect of a finite gain bandwidth is to limit the switching efficiency of the coupler.

© 1991 Optical Society of America