Thermo-optically driven silicon microring-resonator-loaded Mach-Zehnder modulator for low-power consumption and multiple-wavelength modulation

Low-power-consumption thermo-optically controlled silicon-microring-resonator loaded Mach-Zehnder modulators (MRR-loaded MZMs) are demonstrated. We experimentally characterized a single microring and cascaded-multiple-microring resonators coupled to one arm of a Mach-Zehnder interferometer (MZI). The driving power consumption of the proposed MZM is significantly reduced owing to the enhanced phase shift in the MRR. The device was fabricated on a silicon-on-insulator (SOI) waveguide structure, and each microring is equipped with TiN microheater for thermo-optic tuning. The coupling efficiency between the microring and a busline waveguide was regulated by varying the gap between two waveguides at a directional coupler. The power consumption of single microring and cascaded MRR-loaded MZMs was approximately 0.4 and 1 mW, respectively. The phase-shift enhancement factor of up to 19 with a maximum extinction ratio of 18 dB was obtained experimentally. Multiple-wavelength operation was also demonstrated in the cascaded MRR-loaded MZM.