A silicon-on-insulator 2× 2 Mach-Zehnder thermo-optical switch is developed based on strongly guided paired multimode interference couplers. The multimode-interference couplers were etched deeply for improving coupler characteristics such as self-imaging quality, uniformity and fabrication toierance. The proposed switch achieves good performances, including a low insertion loss of -11.0dB, a fiber-waveguide coupling loss of-4.3dB and a fast response speed measured to be 3.5 and 8.8 μs for raise and fall switching time, respectively.
