By  Rob Seal
GPS systems, like those in cars, phones and other devices, could get an upgrade. Photo by Brecht Denil

The next generation of vital communication, radar and other sensing technologies could be much more precise, thanks to groundbreaking new research conducted at the University of Virginia's School of Engineering and Applied Science, published in the journal Nature

Xu Yi, an associate professor in the Department of Electrical and Computer Engineering, helped pioneer a new way to use photonics – or the science of light waves – on a new microchip to create signals with exceptionally low noise. His team included department colleagues professor Andreas Beling, professor Steve Bowers, Shuman Sun (first author), and Beichen Wang (co-first author), as well as professor Dan Blumenthal of the University of California at Santa Barbara, Paul Morton of Morton Photonics Inc. and Karl Nelson of Honeywell International.

“For sensing, communications and many other applications, we must care about signal-to-noise ratio. The lower the noise, the better the signal,” Yi said. “The goal of the research itself is to create microwave and millimeter-wave signals with very, very low noise.”

The implications are vast. Many sensing systems, such as radar for detecting airplanes or satellite-based GPS location systems, operate by sending out a signal, then listening for its return. The return signal gives information about what it found – the location of a whale in the ocean, or a phone’s exact GPS coordinates. But those signals are small and can be overshadowed by noise.

This is especially true for millimeter-wave and microwave signals, which have the promise of carrying much more information – many times more even than Wi-Fi or 5G – but are currently impractical at distances, and one of the reasons is the noise. 

Yi and other researchers already knew that light waves could help improve the signal-to-noise ratio for these frequencies. “It’s because photons don’t interact with the environment much and have very low loss. So, you can have much better quality,” Sun said. Sun is a fifth-year UVA Ph.D. student in the Brown Department of Electrical and Computer Engineering.

But despite the promise of that discovery, the technology hadn’t yet broken through to our phones or computers, Wang said, because no one could shrink the size of the instrument to a microchip for practical use. Wang earned his Ph.D. from UVA in 2023 after finishing this work with Sun and is now a senior photonic design engineer at Analog Photonics, Boston.

“It was great in generating the lowest noise in the world, but you couldn’t really put it on a portable device,” Yi said. 

To tackle that problem, Yi earned a $2.4 million grant from the Defense Advanced Research Project Agency’s GRYPHON program, short for Generating RF with Photonic Oscillators for Low Noise. 

In the resulting project, described in the Nature article, Yi’s team built microchips that used a comb-like structure of light to transfer the ultra-low noise from light to electronic waves (such as microwave and mmWave). The key to the breakthrough is to do everything with photonic chips without compromising the noise. The ultra-low noise light source used in the research is developed by professor Dan Blumenthal’s team at UC Santa Barbara with Morton Photonics and Honeywell International. 

“You now can have a device you can use, a chip-scale device for use anywhere in the world,” Yi said. “It’s much lower noise than electronics, and it can be used like electronics for radar, for global positioning, and in the real world, not just in the lab.” 

Yi said he’s pleased with the result documented in Nature but that he does not consider the research to be concluded. 

“We’re going to continue to push the noise to even lower levels, and also make the implementation simpler,” he said.