Scientists have used an artificial intelligence algorithm to design three components for photonic microchips that are as much as 500 times smaller than conventional versions. The researchers described the results as "beyond human intuition."
Photonic chips move and process data using particles of light instead of electrons. They can carry more data at higher speeds and waste less energy as heat, which makes them useful for fiber-optic networks, data centers, artificial intelligence systems, lidar and quantum computing.
Instead of metal wires, these chips use micrometer-wide channels called waveguides to steer light. They also need wavelength splitters, spatial mode sorters and mirrors to separate and direct light patterns inside a footprint a fraction of the width of a human hair.
Working backward to find a design
The team, led by researchers at the Max Planck Institute for the Science of Light with Harvard University, told the algorithm what they wanted the components to do to light and set manufacturing limits, such as how sharply the nanostructures could curve. The algorithm then worked backward, testing and refining designs until it found structures that met the goal.
"Inverse design lets us define what we want light to do, and the optimization finds a structure that does it, often one no human would have drawn," said first author Toby Bi. He added that the same framework handled three different jobs on one chip: routing light by wavelength, sorting it by spatial mode, and acting as compact mirrors that form optical cavities.
Smaller parts, more room on the chip
The mirrors, about 11 micrometers long, reflected up to 98.5% of incoming light while blocking unwanted patterns. Light bounced between a pair of them more than 100 times before escaping. The wavelength splitter is roughly the size of a single bacterium, about 5 micrometers across, and the mode sorter is slightly larger.
The components were made from silicon nitride roughly 400 to 800 nanometers thick, compared with 150 to 400 nanometers for standard silicon, which cuts light loss and confines wavelengths more tightly. The findings were published May 28 in Nature Communications.
The team has not yet combined the parts into a complete integrated optical circuit. Doing so is the next step toward fully functional photonic chips that take advantage of the higher component density these designs allow.
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