Wafer-scale miniaturized slow-light silicon modulators for 400  Gbps interconnects

Silicon Mach–Zehnder modulators (MZMs) have become indispensable in optical interconnects for data centers and AI clusters due to their robustness and scalability. However, its working principle makes it challenging for silicon MZMs to simultaneously achieve the bandwidth necessary to support 400 Gbps/lambda PAM-4 transmission while maintaining practical modulation efficiency. Here, we present an O-band slow-light silicon MZM leveraging photonic crystal (PhC) waveguides, fabricated on a 300 mm silicon photonics platform. By exploiting the slow-light effect to enhance light–matter interaction, the device achieves a compact footprint of 500 µm, a low half-wave voltage-length product (V π ⋅L) of 0.65V⋅cm, and a high median electro-optic bandwidth of 94.7 GHz. Operated with a 2.7V pp driving voltage, the modulator demonstrates its potential for high-speed, high-density optical interconnects by supporting optical transmission rates of 300Gbps/ λ (135 Gbaud PAM-4) and 400Gbps/ λ (135 Gbaud PAM-8) with a low power consumption of 15.0 fJ/bit.