Soitec (Euronext Paris: SOI) jumped roughly 23% on Thursday — its live quote was up about 24% intraday — after the French wafer maker's fiscal Q1 update blew past its own guidance.

The number that did it: Q1'27 revenue of €113m, up 23% year-on-year at constant currency, against management's own guide of roughly 15%. The engine is Photonics-SOI — the specialty wafers used for high-speed optical transceivers inside AI data centres — where sales doubled year-on-year. The wider Edge & Cloud AI segment did about €65m, up 46%. Then management raised the bar: it guided Q2'27 revenue to grow more than 30% and said Photonics-SOI revenue should more than double FY26's ~$100m.

What it actually means

The same session was a split screen for European chips. While Soitec ripped, STMicroelectronics fell about 15% after a Q2 profit miss tied to a slow auto and industrial recovery, and Dutch tool-maker BE Semiconductor (Besi) slipped ~3% despite strong order bookings. The tell: buyers paid up only for the one name whose growth sits squarely in the AI-optical pocket, and sold the names where either AI upside was already priced in or legacy end-markets still drag.

Soitec sits at the very bottom of the AI-interconnect stack — its SOI wafers are the substrate foundries turn into co-packaged optics and 800G/1.6T optical transceivers. BofA pegs its share of that Photonics-SOI niche above 95%, so as hyperscalers wire up denser GPU clusters that need faster optics, more of that specific wafer demand lands on Soitec; its partner Tower Semiconductor is pouring capacity into the very same technology.

The one risk that flips it

It's a two-speed company. Mobile Communications revenue still fell 10% on smartphone inventory, and the stock has already run to one of Europe's biggest gains of 2026 — so it's priced for the photonics story to keep compounding. The concrete thing to watch is the Q2'27 revenue print: miss that “more than 30%” guide, or show Photonics-SOI slipping off its more-than-double track, and a momentum name can reprice hard — exactly what STMicro's 15% drop showed the same day.

As of 10:08 AM ET / 7:38 PM IST, Jul 23, 2026. Sources: Reuters, MarketScreener. For discussion and education only — not investment advice. Verify before acting.