Non-linear frequency-doubling up-conversion in sulfide minerals enables deep-sea oxygenic photosynthesis

Visible light emission exceeding purely thermal radiation has been imaged at deep-sea hydrothermal vents, yet the underlying mechanisms remain unexplained. Here, we show that visible light can be produced from geothermal infrared radiation via nonlinear frequency-doubling up-conversion in sulfide minerals that are abundant in hydrothermal vents. Chalcopyrite exhibits significant second harmonic generation, which is further amplified under high pressure, yielding a 400-700 nm photon flux three orders of magnitude greater than blackbody emission. When exposed to 1064 nm of irradiation, chalcopyrite induces fluorescence responses in the cyanobacterium <i>Synechococcus</i> sp. PCC 7002 at 656 and 685 nm, suggesting that the up-converted 532 nm light is absorbed by phycobilisomes and transferred to photosystem II. Metagenomic analysis reveals a strong correlation between cyanobacteria and high-temperature, chalcopyrite-rich vents. Similar up-conversion processes have also been observed in other sulfide minerals, emitting wavelengths covering the entire visible spectrum. These findings unveil a novel mineral-mediated photonic mechanism that generates biologically relevant visible light at hydrothermal vents, which can be harnessed by oxygenic photosynthetic cyanobacteria in Earth's deep biosphere and possibly beyond.