Micrometer-Scale Silicon Modulator for O-Band Coherent Interconnects Beyond 100 GBaud

Energy-efficient coherent optics is emerging as a key solution to address the escalating communication demands of large-scale artificial intelligence (AI) and machine learning (ML) tasks. These applications require compact, high-speed, and energy-efficient coherent transceivers. We present an ultra-compact, all-silicon I/Q modulator operating in the O-band, specifically designed for coherent interconnects. The modulator leverages microring-assisted Mach-Zehnder modulators (MRA-MZMs) in a single-drive push-pull configuration, ensuring low-chirp modulation as well as precise electrical phase matching in the push-pull operation. We demonstrate a 6-dB electro-optical bandwidth of 54 GHz and achieve QPSK modulation at speeds up to 120 Gbaud, resulting in a net bit rate of 200 Gbps per wavelength and polarization. With its compact design, the modulator achieves a bandwidth density of 2 Tbps/mm. Furthermore, its versatile architecture supports wavelength division multiplexing and dual-polarization, enabling further capacity expansion.