Researchers at Stanford University have developed an optical device that allows engineers to change and fine-tune the frequencies of each individual photon in a stream of light to virtually any mixture of colors. The optical device is based on a new photonic architecture that could transform fields ranging from digital communications and artificial intelligence to cutting-edge quantum computing.
"This powerful new tool puts a degree of control in the engineer's hands not previously possible," said Shanhui Fan, a professor of electrical engineering at Stanford and senior author of the paper, published in Nature Communication.
The structure consists of a low-loss wire for light carrying a stream of photons that pass by like cars on a busy throughway. The photons then enter a series of rings, like the off-ramps in a highway cloverleaf. Each ring has a modulator that transforms the frequency of the passing photons. There can be as many rings as necessary, and engineers can finely control the modulators to dial in the desired frequency transformation.
Among the applications that the researchers envision include optical neural networks for artificial intelligence that perform neural computations using light instead of electrons. Existing methods that accomplish optical neural networks do not actually change the frequencies of the photons, but simply reroute photons of a single frequency. Performing such neural computations through frequency manipulation could lead to much more compact devices, say the researchers.
"Our device is a significant departure from existing methods with a small footprint and yet offering tremendous new engineering flexibility," said Avik Dutt, a post-doctoral scholar in Fan's lab and second author of the paper.