Coherent Stock Tumbles 12% Ahead of Wednesday Earnings as AI Optics Sector Cools and Optics vs. Memory Debate Heats Up

Coherent (COHR) shares fell roughly 11.6% to approximately $335 on Monday, August 10, sliding from Friday's close of $379.13 as traders took profits across the AI optics complex ahead of a pivotal earnings report. Lumentum (LITE) dropped about 7% to $830.05 in the same session, with both names pressured by pre-earnings de-risking rather than a broad market selloff. A weekend social media debate pitting AI optics against memory as the more critical AI hardware buildout theme added to the selling pressure.

The earnings calendar is a central factor: Lumentum reports its fiscal fourth quarter 2026 results after the close on Tuesday, August 12, and Coherent follows with its own fiscal Q4 2026 report after Wednesday's close. In a related development, Aura ETF launched the Aura VettaFi Photonics Index ETF (PHOX) on Monday, targeting the AI optics infrastructure theme that has driven the sector's sharp year-to-date gains.