The AI boom is running into a copper problem

Lightmatter CEO Nick Harris

Lightmatter

Silicon Valley's AI infrastructure boom has created a surprisingly physical problem: there's only so much data you can push through copper wires before heat, distance, and power consumption become overwhelming.That's why investors, chipmakers, and cloud giants are suddenly paying close attention to photonics, using light instead of electrical signals to move data between AI chips and servers.I recently visited Lightmatter's Silicon Valley headquarters, where the startup demonstrated its latest photonics hardware for AI data centers. After the event, I sat down with Lightmatter CEO Nick Harris to talk about why optics may become essential infrastructure for the AI era.Harris looks annoyingly young and he's annoyingly bright, with a Ph.D. from MIT. And Lightmatter is already annoyingly successful, having raised $850 million from huge backers including Google, Fidelity, and T. Rowe Price.On Tuesday, Lightmatter joined Nvidia's NVLink Fusion ecosystem, which should help the startup's technology work better with Nvidia's dominant AI hardware.Here's my conversation with Harris, lightly edited for clarity and length.Q: Why are AI companies suddenly interested in photonics?Harris said the AI industry has reached a point where scaling performance is less about making individual chips faster and more about connecting huge numbers of GPUs together efficiently.