Submilliwatt thermo-optic switches using free-standing silicon-on-insulator strip waveguides

A low power Mach-Zehnder interferometer thermo-optic switch using free-standing silicon-on-insulator strip waveguides is demonstrated. The air gap provides thermal isolation between the waveguide interferometer arms and the underlying silicon substrate. The highly confined optical modes of the strip waveguides enable miniature heated cross-sections. The heating efficiency from on-chip resistive heaters is enhanced. Measurements of fabricated devices using 100 microm arm lengths at 1550 nm wavelength result in a switching power of 540 microW, a 10% - 90% switching rise time of 141 micros, and an extinction ratio of 25 dB.