Low-power compact 2×2 thermooptic silica-on-silicon waveguide switch with fast response

5-mm-long and 50-μm-wide thermooptic waveguide 2×2 Mach-Zehnder interferometer (MZI) switches with multimode interference (MMI) couplers have been realized in silica-on-silicon. The use of diffused square waveguides with a separating trench results in low heating power of 110 mW for /spl pi/ phase shift and short rise and fall times of 150 and 180 μs, respectively.