200 Gb/s All-Silicon Photodetection Enabled by Response-Engineered Tandem Microrings

High-speed, compact photodetectors are essential for silicon photonics. Germanium and III–V materials are well-established for integrated photodetection. However, the heterogeneous integration with silicon waveguides generally increases cost and fabrication complexity. All-silicon photodetectors offer a monolithic alternative, but their performance is fundamentally constrained by the transparency of silicon at telecom wavelengths and the intrinsic trade-off between responsivity and bandwidth. Here, we propose and experimentally demonstrate a response-engineered tandem microring photodetector that overcomes this limitation. By detuning resonances to form a partially overlapped dual-peak response, the device can support strong optical field enhancement and large optoelectronic bandwidth. The foundry-fabricated photodetector exhibits a 3 dB bandwidth of 40 GHz, a responsivity of 0.32 A/W, and a dark current of 300 nA at −8.4 V bias. Record-high data reception rates of 128 Gb/s NRZ and 200 Gb/s PAM-4 are experimentally demonstrated, showing the potential of this approach for high-speed optical interconnects.