China develops laser radar that can 'find a needle in a haystack'

Xiamen University's lidar (laser radar) system can operate at a depth of one kilometer and detect oil spills from a distance of 12 meters .

A team of researchers from Xiamen University has developed a single-photon Raman lidar system . This radar technology can detect objects at great depths with such clarity that it is like "finding a needle in a haystack , " Interesting Engineering reported on December 10. The new technology is highly sensitive, uses low-noise single-photon detectors, and is useful for underwater sensing activities such as ocean surveys, oil spill detection, and deep-sea resource exploration.

Single photon Raman lidar system. (Photo: Xiamen University).

The device developed by researcher Mingjia Shangguan and his colleagues is notable for its relatively small size, low power consumption, and ability to operate at depths of 1,000 meters below sea level. It is so sensitive that it can analyze the thickness of an oil spill as far as 12 meters away, using only one microjoule laser pulse . According to Shangguan, distinguishing substances in water and detecting their distribution characteristics in the ocean is of great importance for marine environmental monitoring and scientific research. For example, remote oil sensing helps track leaks in underwater oil pipelines.

Traditional lidar systems, typically used on ships, aircraft, or satellites, can scan the ocean at large scales. However, their ability to detect at great depths is limited, especially in rough sea conditions. In contrast, Raman lidar systems can analyze underwater environments at a wide range of depths without being affected by sea conditions. Raman lidar works by emitting a pulse of green laser light into water, where it interacts with a material such as oil. This interaction produces an inelastic Raman signal that can be used to identify different materials. By measuring the intensity of the Raman signal at a specific wavelength, lidar can provide information about the oil content of the water.

China's new lidar system is 40 centimeters long and 20 centimeters in diameter, allowing it to operate effectively at depths of 1,000 meters. To enhance sensitivity, the team has integrated single-photon detection capabilities into the underwater Raman lidar system. "Placing the Raman lidar system on an autonomous or remotely operated vehicle could help track leaks or be used for resource exploration and coral reef detection ," Shangguan said.

Because the technology allows for high-resolution laser imaging of small underwater targets, it has potential applications in underwater archaeology, construction inspection, military operations such as reconnaissance and submarine detection. The team's next plan is to develop underwater Raman lidar using shorter wavelength lasers such as blue lasers and integrate it into autonomous vehicles.