Silicon microdisk modulator with 67 GHz bandwidth and fJ/bit power consumption

The advancements of silicon photonics modulators provide a promising solution to establish high-speed and energy-efficient optical links in data centers. Intra-rack optical interconnects have rigorous requirements on both bandwidth density and power consumption. Silicon microdisk modulator shows unique advantages of compactness and low power consumption, while it is more tolerant to sidewall roughness scattering than its counterparts, such as microring structures. Thus, it can be designed with a much smaller size to achieve a wider free spectral range and accommodate more wavelength channels. However, this will result in much weaker coupling strength between the bus waveguide and the cavity, leading to difficulty in optimizing the quality factor and extinction ratio. Here, we propose and experimentally demonstrate a silicon microdisk modulator with a curvature-engineered boundary to optimize the quality factor and the coupling strength simultaneously. The device achieves a recorded 3-dB bandwidth of 67 GHz, supporting a data rate up to 196 Gbps with a power consumption of 1.3 fJ/bit.