Ultracompact and large-bandwidth silicon modulator in a CMOS-compatible foundry.

The exponential growth of global data traffic demands transformative solutions for data centers. While optical interconnects offer a promising pathway to overcome the bandwidth limitation, conventional electro-optic modulators face a bandwidth-footprint trade-off. Here, we demonstrate a silicon modulator by leveraging the slow-light effect in a photonic crystal nanobeam cavity. The proposed modulator exhibits a 110-GHz electro-optic bandwidth with an ultracompact footprint of 10 µm² while enabling precise light manipulation with an 80 pm/V tuning efficiency within a 0.12 µm³ mode volume. We also demonstrate 110-Gbps and 130-Gbps non-return-to-zero signal transmissions with bit error rates less than 3.8 × 10⁻³ and 2 × 10⁻², respectively, while maintaining a power consumption of 5.9 fJ/bit. This breakthrough represents an important advance in photonic interconnect technology, as it overcomes the critical trade-off between bandwidth and footprint while achieving an ultra-high energy efficiency, thereby paving the way for next-generation ultracompact, high-speed, and energy-efficient optical interconnects in data centers and beyond.