Active waveguides at transparency for ultrafast all-optical switching

The authors have demonstrated large phase shifts in active semiconductor waveguides with recovery times in the picosecond range and at power levels accessible to simple laser sources. They have demonstrated partial all-optical switching in a nonlinear directional coupler exploiting this effect. The present devices are limited by their high internal loss, and reducing this will improve the performance of the present devices considerably. With this and further optimisation this approach offers the prospect of all-optical switching in the 100 Gbit/s regime at moderate power levels