​Atmospheric LiDAR instruments can be used on board satellites to monitor the atmospheric canopy, winds, and greenhouse gas concentrations and distributions. The detectors inside these instruments are specific to a single wavelength, which means that they can only measure one thing. Given the huge costs and long turnaround times associated with certifying instruments for space, atmospheric LiDAR deployment remains relatively limited. CEA-Leti is helping develop a robust and versatile device that can detect all wavelengths for the EU Holdon project. The goal is to deliver the required sensitivity and signal dynamics for a variety of applications in a single detector.

HgCdTe avalanche photodiodes (APDs), one of CEA-Leti's areas of expertise, give the detector a high degree of sensitivity, amplifying the signal 100-fold with only a small increase in noise, for nearly single-photon detection sensitivity. An ultra-high dynamic range CMOS circuit was also designed specifically to meet the most stringent LiDAR sensitivity, dynamic range, and time resolution requirements. The research showed that, together, the APDs and CMOS circuit effectively collect light signals of various intensities. In this research, the device was able to measure a range of up to six to seven orders of magnitude.

Demonstrators built for the project are now on their way to several labs and a manufacturer for testing. With unprecedented sensitivity and dynamic range over a wide range of wavelengths, this high-performance device is expected to be able to address a significant number of use cases. And, once the detector has been qualified for space, it will help democratize the use of LiDAR on space missions.