A Chinese radar research team’s scientific paper that plumbed new depths of underwater discovery has been recognised in this year’s awards from the international journal Applied Optics.
The paper, which stood out among 1,278 submissions to the journal’s Best Paper Prize in October, introduced a radar technology that can detect objects at great depths with such clarity it has been likened to “fishing for a needle in the sea”.
The researchers, led by Xiamen University associate professor Shangguan Mingjia, unveiled the world’s first single-photon Raman lidar system in the 2023 paper, capable of operating at 1,000 metres (about 3,280 feet) below sea level.
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Short for “light detection and ranging”, lidar sensors use lasers to measure the distance to objects.
The highly sensitive, low-noise single-photon detector beats the significant size and power consumption challenges of oceanic lidar systems and is also suitable for lowlight conditions.
Meanwhile, Raman scattering – the phenomenon of laser light interacting with materials to produce vibrational changes – can help to identify substances such as oil and dissolved CO2, according to the paper.
Beyond early detection of oil spills, the system shows immense potential for detecting and identifying materials in complex aquatic environments, with applications in ocean surveys and deep-sea resource exploration.
According to the paper, the team’s experimental demonstrations were based on a 40cm (about 15.7 inches) long cylindrical radar with a diameter of 20cm (about 7.87 inches) and a power consumption of under 100 watts.
The researchers reported that the radar successfully detected underwater oil spills from a distance of 12 metres (about 39.4 feet) using just a 1-microjoule laser pulse and a 22.4mm telescope.
A special report on the radar system by Optica, a professional society in the US, noted that it can be deployed at depths of up to 1,000 metres and said it was characterised by miniaturisation and high integration.
According to the Optica report, the system has significant potential applications in underwater material identification, coral detection, and manganese nodule exploration.
Since the technology provides a chance for high-resolution laser imaging of small underwater targets, it could have potential uses in underwater archaeology, structural inspections, and military fields such as reconnaissance and submarine detection.
Writing in the paper, Shangguan said the team’s next plan is to develop “another underwater Raman lidar using a shorter-wavelength laser, such as a blue laser, to reduce the influence of chlorophyll fluorescence from marine plants”.
“Additionally, we will integrate [the system] into autonomous underwater vehicles (AUVs),” he said.
Shangguan and his team at the National Key Laboratory for Coastal and Ocean Environmental Science have been focused on developing underwater single-photon lidar technology for the past three years.
They have already created several lidar systems and filed 50 national invention patents as well as one US patent.
According to an official report from Xiamen University, the team’s radar technology can detect optical properties of water, water particle profiles, bubbles, water depth, oil spills, and more.
“Such radar systems have already been integrated into Xiamen University’s Jia Geng research vessel, AUVs and drones, playing a key role in marine surveys, deep-sea resource exploration, environmental monitoring, and underwater target imaging and recognition,” it said.
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