Silicon photonics for AI chips

A $300 million award to GlobalFoundries under the CHIPS and Science Act targets a specific bottleneck in AI hardware: interconnect bandwidth. Most commentary around government chip funding focuses on leading-edge logic nodes, but this grant is different — it's a direct bet on silicon photonics as the solution for moving data between accelerators.

For anyone who hasn't followed the tech, silicon photonics replaces electrical traces with optical waveguides etched directly into silicon chips. Light carries data at higher bandwidth over longer distances with a fraction of the power consumed by copper connections. In AI training clusters, where communication between thousands of GPUs can stall the computation, that efficiency gain is huge.

Why silicon photonics matters for AI

• Bandwidth density: Optical interconnects can pack many wavelengths (DWDM) into one fiber, scaling without requiring more pins or PCB area.
• Power reduction: Driving a laser uses less power than pushing signals through lossy copper traces at high data rates.
• Reach: Optical signals degrade less over meters, making rack-scale and pod-scale interconnects viable without repeaters.

These characteristics directly address the memory wall and communication bottleneck that limit scaling in large models. Without better interconnects, compute utilization drops as the model grows.

What this funding actually enables

GlobalFoundries already runs a silicon photonics platform on 300mm wafers at its Fab 8 in Malta, New York. The $300M will accelerate process development and likely fund specific milestones — think lower insertion loss for modulators, higher integration density for laser attach, and better yield for co-packaged optics. The award mentions "bolstering fabrication capabilities," which could mean new equipment for wafer-scale testing or hybrid bonding lines that combine photonic and electronic dies.

What I find interesting is the strategic choice. Intel is pushing its own integrated photonics with the Picasso project. TSMC is developing a photonics platform called COUPE. By funding GlobalFoundries — an independent foundry without its own CPU/GPU products — the