Photonic wire bonding: a novel concept for chip-scale interconnects

TLDR

Photonic integration has advanced to Terabit/s chip‑scale transceivers, but rising on‑chip density demands efficient off‑chip interfaces, making a breakthrough in short‑distance optical interconnects essential. This letter introduces photonic wire bonding, a method that uses transparent waveguide wire bonds to connect nanophotonic circuits on separate chips. The authors fabricate three‑dimensional freeform photonic wire bonds that physically bridge the gap between chips, enabling broadband coupling. They demonstrate the viability of these bonds in a multi‑Terabit/s transmission experiment, achieving broadband coupling with only 1.6 dB loss and enabling flexible multi‑chip assemblies that challenge monolithic integration.

Abstract

Photonic integration has witnessed tremendous progress over the last years, and chip-scale transceiver systems with Terabit/s data rates have come into reach. However, as on-chip integration density increases, efficient off-chip interfaces are becoming more and more crucial. A technological breakthrough is considered indispensable to cope with the challenges arising from large-scale photonic integration, and this particularly applies to short-distance optical interconnects. In this letter we introduce the concept of photonic wire bonding, where transparent waveguide wire bonds are used to bridge the gap between nanophotonic circuits located on different chips. We demonstrate for the first time the fabrication of three-dimensional freeform photonic wire bonds (PWB), and we confirm their viability in a multi-Terabit/s data transmission experiment. First-generation prototypes allow for efficient broadband coupling with overall losses of only 1.6 dB. Photonic wire bonding will enable flexible optical multi-chip assemblies, thereby challenging the current paradigm of highly-complex monolithic integration.