Femtosecond all-optical switching using efficient incoherent nonlinearity with slow relaxation

We describe ultrafast all-optical switching experiments with the symmetric Mach-Zehnder (SMZ) all-optical switch proposed by the authors. A switching speed of 800 femtoseconds (fs) has been achieved, which was limited only by the very large group velocity dispersion of the fiber components used in the experiment. We have also experimentally shown that high repetition operation, much faster than that implied by the relaxation time of nonlinearity, is possible. We examine various factors that possibly limit the switching speed and conclude that a switching speed approaching 100 fs can be expected. We also point out that the well-known figure of merit for optical nonlinear materials is no longer applicable to the present device, because its operation is new and different from conventional all-optical switches.