Thermo-optic phase shifter with sub-microsecond switching time and low power consumption

We propose a thermo-optic phase shifter utilizing multimode interference in a silicon waveguide. The electrodes were attached to the section where the multimode interference had the minimum optical electric field around the sidewalls. We designed the multimode waveguide width to reduce optical propagation loss in the C-L wavelength band (1.53-1.625 μm). We succeeded in developing a low optical loss thermo-optic phase shifter with less than 0.1 dB in the wavelength range of 1.5 to 1.6 μm. Moreover, wavelength dependence was reduced by adjusting the number of electrodes. An optical switch with the designed thermo-optic phase shifter was fabricated and used to estimate the optical switching time. Switching time of several microseconds was obtained by normal pulse operation, and ultrafast optical switching of about 500 ns was realized by overdrive control.