Integrated silicon elliptical ring modulator with ultra-high bandwidth beyond 110 GHz

Optical interconnects have been considered as an enabling technique for energy-efficient and high-throughput optical I/O. Silicon photonic microring modulators are one of the fundamental building blocks for optical I/O due to their inherent advantages of compactness, energy efficiency, and compatibility to wavelength-division multiplexing. High-speed microring modulators normally require a bending radius as small as possible to reduce the resistance-capacitance constant. However, this will result in weaker bus-ring coupling and increased cavity loss, which eventually leads to difficulty in optimization of quality factor and extinction ratio. Here, we demonstrated an elliptical silicon ring modulator with enhanced bus-ring coupling strength. The device exhibits a high extinction ratio of 32 dB and a 3-dB electro-optic bandwidth beyond 110 GHz, supporting up to 112 Gbaud PAM-4 modulation.