[OFC 2026] Part 3 of 5: Packaging: Glass Substrates to 3D Hybrid Bonding

Key Takeaways

• Glass substrates reduce signal loss in CPO
• Hybrid bonding eliminates solder, improving thermal performance
• InP‑on‑Si PIC solves L‑band receiver trade‑off
• Packaging choice directly impacts bandwidth and power

Pulse Analysis

The rapid expansion of AI workloads has shifted the performance ceiling from transistor speed to the interconnects that shuttle data between chips. Co‑Packaged Optics (CPO) addresses this by embedding lasers and detectors inside the same package as the switch ASIC, dramatically shortening electrical paths and cutting power consumption. However, the success of CPO hinges on the underlying substrate material and the method used to attach photonic and electronic dies, as any mismatch can introduce loss, thermal hotspots, or reliability concerns.

Corning’s glass platform, presented at OFC, leverages ultra‑low‑loss silica to create a thermally stable, electrically insulating base for CPO modules. Glass offers superior optical transparency compared with traditional silicon interposers and can be processed with high‑precision planarization, enabling tighter pitch and finer waveguide routing. Early prototypes demonstrate reduced insertion loss and improved thermal management, positioning glass as a compelling alternative for high‑density data‑center optics where every decibel counts.

Beyond glass, UC Davis and Lawrence Berkeley National Lab unveiled a 3‑D hybrid‑bonded EPIC that completely removes solder, using direct metal‑to‑metal bonding to achieve sub‑micron alignment and superior heat extraction. Meanwhile, Sumitomo’s PETRA team delivered an InP‑on‑Si photonic integrated circuit that resolves the long‑standing L‑band coherent receiver trade‑off through heterogeneous integration. These advances illustrate a broader industry shift toward solder‑free, heterogeneous packaging solutions that promise higher bandwidth, lower latency, and scalable manufacturing—key factors that will shape the competitive landscape of AI‑centric data centers.