Submicrosecond submilliwatt silicon-on-insulator thermooptic switch

Mach-Zehnder interferometer thermooptic switches were made using a thin-silicon-on-insulator material system. The switches use single-mode strip-Si waveguides, 0.26×0.4 μm, operating at 1.5 μm. The waveguides were heated directly by passing current through them, resulting in switching power of 6 mW, and a rise time of 0.6 μs. By heating both arms of the interferometer differentially, so one arm is cooling while the other heating, the switching-signal input power is reduced to <100 μW. In this differential mode, the switching time can be decreased to 50 ns by pulsing the electrical input to 10 mW. Modeling indicates 10-ns-switching time would require /spl sim/23 mW of pulsed power.