Abstract

Recently we have demonstrated the highspeed switching capabilities of a novel symmetric Mach-Zehnder (SMZ) all-optical switch.^1,2 Figure 1(a) shows the schematic of the SMZ all-optical switch. Both arms of a Mach-Zehnder interferometer have nonlinear waveguides in which a nonlinear refractive index change is induced by the photoexcited band-filling effect. Two control pulses are injected into the corresponding nonlinear waveguides at an appropriate time interval. The first control pulse absorbed in the nonlinear waveguide 1 induces the switching of the signal light output from one port to the other (switch-on). Then, the second control pulse excites the nonlinear waveguide 2, canceling the effect of the refractive index change induced by the first control pulse and switching the signal light back (switch-off). Ultrafast switching as short as 1 ps can thus be expected, although the utilized band-filling effect relaxes on a nanosecond time scale. We have experimentally shown that full switching is possible with control pulse energies of less than 7 pj per waveguide at a detector-limited switching time of 8 ps.² In addition, we have theoretically predicted the possibility of high-repetition operation of more than several 10 GHz, although the experimentally shown repetition rate was 82 MHz. In this report, we experimentally demonstrate high-repetition switching using a series of four control pulses at intervals of 100 ps or 25 ps.

© 1995 IEEE