Photonic Wire Bonding: Bridging the Gaps in Photonic Packaging

Expert: Dr.Wojciech Lewoczko-Adamczyk

Photonic wire bonding (PWB) is a novel technology for interconnecting photonic integrated circuits (PICs) to optical fibers and semiconductor laser emitter.

The primary goal is to realize low-loss optical interconnects between different classes of waveguides and to correct for the technical placement uncertainty of the die-bonding process. Thus, PWB allows for passive die bonding, without the necessity of active alignment of the waveguides to each other. 

PWBs are created in a  two-photon polymerization (2PP) process – a form of 3D laser direct writing lithography. Nonlinear two-photon absorption is initiated in a liquid, photopolymerizable resist by a tightly focused femtosecond laser pulse. This enables polymerization (curing) of the material exclusively in the tiny volume (voxel) within the focused beam.
PWB -  indispensable for high-performance hybrid photonic systems

The performance of PWB is demonstrated by the following metrics:

• Fiber-PIC coupling efficiency: optimized free-form geometry enables coupling losses less than 2 dB in the C-band range per coupling interface.
• Hybrid integration:  PWBs enable the hybrid integration of PICs manufactured on different platforms such as InP, SOI, SiN, LiNbO3 and glass. They support a wide range of coupling configurations (PIC-to-PIC, laser-to-PIC, laser-to-fiber and PIC-to-fiber).
• Tolerance compensation: The technology compensates for positional uncertaincies of up to ±30 µm, which greatly reduces die assembly efforts.

PWB is thus establishing as a scalable and automated packaging solution that is indispensable for high-performance hybrid photonic systems in data communication and on-chip sensing.