Heriot-Watt nanowire detector boosts lidar performance

11 Feb 2025

Improved depth imaging and intensity will help security and defense applications.

A project led by Heriot-Watt University has developed a novel single-photon detection system set to improve the performance of lidar systems.

Described in Optica, the detector "can generate high-resolution three-dimensional images with double the efficiency of similar lidar systems, and at least 10 times better image resolution."

The performance enhancements available to lidar systems from improved detection and sensor devices have already been put to use in applications where a lidar approach might otherwise struggle.

Previous work at Heriot-Watt included the 2023 demonstration of single-photon detection regimes able to operate underwater, designed specifically to tackle the issues of scatter and distortion inherent in that environment.

The new work looked in particular at adopting superconducting nanowire single-photon detectors (SNSPDs), a class of sensor whose fast detection speeds have been used to improve the sensitivity of diffuse spectroscopy methods among other techniques.

A SNSPD developed by Massachusetts Institute of Technology and NASA's Jet Propulsion Laboratory was employed in the new study, cooled in use to 272 degrees Celsius, or 1 Kelvin, so as to become superconducting and demonstrate no electrical resistance when a photon lands on it.

"SNSPDs have arguably become the gold standard in single-photon detection," commented the project in its paper. "But no deployment in the field of single-photon lidar has yet been reported."

Tanks spotted at ten kilometers

In trials, the new 1550-nanometer lidar platform was mounted on the roof of Heriot-Watt's lab and directed at targets located 45 and 325 meters away. Along with a number of building features and 3D-printed reference boards, the platform was also directed towards a member of the project team standing at the same locations.

Results showed that 1-millimeter depth features on a reference board and a human head were clearly resolved when measured by the system in broad daylight at both 45 and 325 meters standoff distances. Per-pixel acquisition times of between 0.25 and 1 millisecond were measured.

These numbers suggest that the system could lend itself to facial and human activity recognition applications at distances up to 1 kilometer, commented the Heriot-Watt project. But greater distances could be possible: in theory the system's illumination spot could be 150 millimeters in diameter at 10-kilometers distance, which would allow identification of vehicle types that far away in modest levels of atmospheric turbulence.

Since only a few tens of target returned photons are potentially required to reach the SNSPD to form high-resolution depth images, the platform could also lead to improved imaging of scenes behind clutter, around obstacles or in turbid media.

"Could we recognize a vehicle type at 10 kilometres, whether it's a car or a van or a tank?" commented Aongus McCarthy from Heriot-Watt’s Institute of Photonics and Quantum Sciences (IPAQS).

"The results of our research show the enormous potential of such a system to construct detailed high-resolution 3D images of scenes from long distances in daylight or darkness conditions. So there are a number of potential applications from a security and defense perspective."