Differential Microring Modulators for Intensity and Phase Modulation: Theory and Experiments

We theoretically and experimentally demonstrate a ring-assisted Mach-Zehnder interferometer modulator for intensity and phase modulation, leveraging both Mach-Zehnder modulator and single microring modulator. Differential drive of two microring modulators nested in a Mach-Zehnder interferometer offers several advantages for both intensity modulation and phase modulation. We first present a complete theoretical study of this differential ring modulator, including the operation principles, high-speed characteristics, system performance, and energy consumption. We then experimentally verify that this differential ring modulator provides low-chirp, low drive voltage, and large extinction ratio for intensity modulation, and low-chirp, low drive voltage, and drive-voltage insensitivity for phase modulation.