Photonic Wirebonds: The Future of Flexible, High-Performance Chip-to-Chip Connectivity?
Our followers on LinkedIn recently voted photonic wirebonds as the most exciting advance in fibre-to-chip packaging today.
Photonic wirebonds are a way to physically and optically connect different photonic chips or optical components—similar in spirit to how metal wirebonds connect electronic chips, but using tiny 3D waveguides instead of metal wires.
The process typically uses two-photon polymerization (TPP), a high-resolution 3D laser lithography technique:
Chips are placed near each other with relaxed alignment tolerances (a few micrometers)
A focused femtosecond laser writes the desired waveguide shape directly into a photoresist
The resist is developed, leaving behind a freeform optical waveguide that matches the on-chip waveguides
This is like drawing a custom optical bridge in mid-air between the two photonic circuits
This is good for a few reasons:
💪 High coupling efficiency: Losses can be <2 dB per interface
💪 3D freedom: Can route light over various heights, angles, and lateral offsets
💪 Material independence: Can connect Si, InP, SiN, LiNbO₃, or others
💪 Relaxed positioning tolerances: No need for sub-micron chip placement
💪 Scalable packaging: Useful for multi-chip photonic modules
But this solution is not without its challenges. If you’re planning on using this, there are a few potential issues you need to be aware of:
🚨 For fibre-to-chip connections in mass production, you may need thousands of bonds per wafer/module, and TPP’s speed can be orders of magnitude too slow compared to lower spec. passive align-and-glue methods
🚨 Even with parallelised or faster writing systems, scaling to tens of millions of connections a year is a serious challenge
🚨 Every connection requires 3D position measurement and adaptive path generation, which increases process complexity
🚨 Photonic wirebonds are polymer-based waveguides. Polymers can suffer from ageing, UV exposure sensitivity, water uptake, and thermal expansion mismatch — especially under telecom-grade environmental tests.
🚨The absorption profile of the PWB material may limit the wavelengths you can use.
Photonic wirebonds are most promising for chip-to-chip optical interconnects in heterogeneous photonic integration, where different material platforms—like InP lasers, silicon photonics modulators, and LiNbO₃ devices—need low-loss, flexible, and precisely aligned optical connections.
They enable custom 3D waveguide bridges that overcome strict alignment tolerances, making them ideal for multi-chip photonic modules, and specialised low-volume systems as in quantum photonics or aerospace applications.
While slower than traditional methods, their ability to connect diverse chips with high optical performance and relaxed mechanical constraints makes them highly valuable in advanced photonic packaging scenarios where performance and flexibility outweigh throughput.
How do you see photonic wirebonds shaping the future of integrated photonics? Are they the game-changer for heterogeneous chip integration, or will other technologies take the lead?
