Packaging Photonic Integrated Circuits: The Last Millimeter Problem

A photonic integrated circuit (PIC) can generate, modulate, and detect light across dozens of channels on a chip measuring just 5mm × 10mm. The waveguides on that chip confine light in structures barely 200nm wide. Yet to be useful, that chip must connect to the outside world through standard 125μm diameter optical fibers — a scale mismatch of nearly 1000:1. This "last millimeter" — the physical gap between chip and fiber — is where most of the cost, complexity, and failure risk in photonic packaging resides.