Physicists at the University of Pennsylvania have coupled light and two-dimensional material into a nanometric cavity, opening a trail to very sober photonic AI chips.
Light carries information very quickly but interacts poorly with itself, forcing optical circuits to go back to electronics for any logical operation — and that's precisely where the energy goes. Bo Zhen's team at the University of Pennsylvania sought to eliminate this back and forth.
By injecting light into a nano-sized cavity in contact with atomic-thick material, the researchers created exciton-polaritons: hybrid quasiparticles that retain the speed of the photon while inheriting the interaction capacity of matter. They demonstrated an all-optical switching that consumes about 4 millionths of a billionth of a joule, far below what is required to briefly ignite a tiny light-emitting diode.
If the process can be scaled up, it paves the way for photonic chips capable of directly processing the signal from an image sensor, without repeated conversions between light and electricity — with the key to reducing the energy bill of large AI systems, and even of the elementary quantum functions on board. The work, by Li He, Zhi Wang and Bumho Kim and funded by the Office of Naval Research and the Sloan Foundation, was published in Physical Review Letters.
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