Indium phosphide

Indium phosphide is a specialty crystal material from which the lasers inside optical modules are grown. It sits upstream of almost everything in high-performance optics — the semiconductor substrate on which light-emitting and light-detecting structures are built, several steps below the transceivers that stitch AI clusters together. It matters because a very small material can govern a giant system: without the right substrate you cannot make the lasers, and without the lasers you cannot make the optics that move data between accelerators. Concentrated supply and export-control attention have turned it into a strategic pressure point for the whole photonics stack.

If indium phosphide tightens — through export restrictions or a supply shock — the effect cascades upward, since a shortage of the base material caps how many lasers and modules can be built regardless of downstream capacity. Geographic concentration makes this a form of strategic leverage. The names most exposed are the substrate and laser specialists — Coherent, AXT, LandMark Optoelectronics, Visual Photonics Epitaxy — alongside module makers such as Lumentum that depend on the material flowing through.