Stopwatch offers heightened precision for imaging, others

A newly developed stopwatch, touted one of the most precise to date, is allowing researchers to count single photons. This has the potential to improve and enhance a number of imaging technologies.

In their study, researchers at the University of Colorado Boulder (CU Boulder) focused on a widely applied technology: time-correlated single-photon counting (TCSPC). The researchers say this works similar to stopwatch timers used for runners during the Olympics. First, a laser light illuminated samples ranging from individual proteins to a massive geologic formation. Next, they were able to record any photons that bounce back.

“TCSPC gives you the total number of photons,” says Bowen Li, a postdoctoral researcher in the Department of Electrical, Computer, and Energy Engineering (ECEE) at CU Boulder who was the lead author of this study. “It also times when each photon hits your detector. It works like a stopwatch.” Li notes that the stopwatch has advanced, thanks to an ultrafast optics tool called a “time lens.” The researchers have demonstrated the ability to measure the arrival of photons “with a precision that’s more than 100X better than existing tools.”

According to Shu-Wei Huang, an assistant professor at CU Boulder’s ECEE who participated in the new study, this quantum time lens could be easily adaptable. “We can add this modification to almost any TCSPC system to improve its single-photon timing resolution.”

The findings could potentially improve a wide range of imaging technologies, from sensors that can map entire forests and mountain ranges to more detailed devices, including those that diagnose human diseases such as Alzheimer’s and cancer. The researchers are hopeful, too, that the new stopwatch tool will allow humans to view objects with “all with a clarity that was previously impossible.” Reference: B. Li, J. Bartos, Y. Xie, and S.-W. Huang, Optica, 8, 8, 1109–1112 (2021).