Integrated photonics narrows the gap between laboratory result and manufacturable part

Photonics research has never lacked impressive demonstrations. What it has historically lacked is a reliable route from a working device on an optical table to something a company can order in quantity. That route is now being built, and it looks familiar to anyone who watched semiconductors industrialise.

Foundries and process design kits

The central change is the availability of shared foundry processes for photonic integrated circuits. A research group or startup can design to a documented set of building blocks — waveguides, couplers, modulators, detectors — with characterised performance and tolerances, and have the design fabricated alongside other users' work.

The process design kit is what makes this more than a fabrication service. By fixing what is available and specifying how each element behaves, it lets designers simulate a circuit with reasonable confidence that the manufactured device will match. That single abstraction is what turned electronic design from a craft into an industry, and it is now doing similar work in photonics.

Where the platforms diverge

Silicon photonics has the deepest ecosystem, inheriting mature CMOS fabrication and offering dense integration with electronics. Its weakness is well known: silicon is a poor light emitter, so lasers usually have to be bonded on rather than grown in place, and that hybrid integration step is a persistent cost and yield concern.

Silicon nitride offers exceptionally low propagation loss and broad transparency, making it attractive for sensing, frequency combs and quantum work, at the cost of weaker electro-optic modulation.