Differential Absorption Lidar

Broadband differential absorption lidar (DIAL) combines lidar and absorption spectroscopy technologies to identify and quantify air pollutants at short range. It can also remotely identify solid and liquid substances on a variety of surfaces.

The spectral-band-optimized-laser (<1 nm to >100 nm), multipixel sensor (range-gated at 10 nanoseconds or more), and associated spectrograph provide simultaneous, sensitive identification of numerous pollutants. The laser system can be tuned from 1.3 to 5 µm as gain medium period or temperature are changed. The platform can detect molecules with SWIR and MWIR signatures. These characteristics lead to improved selectivity when identifying and quantifying gases and reduce the negative impact of the atmospheric instabilities observed with DIAL measurements that use only two successive wavelengths.

The platform can operate in spatially and spectrally resolved mode with a rapid HgCdTe detector and laser injection.

The platform can be used in the field.

Our expertise: Differential absorption lidar

  • Design and fabrication of spectroscopic lidar systems that generally include a spectrograph and range-gated camera or a custom detection system, optimized optics, and a light and stable optomechanical structure

  • Remote identification and quantification of air pollutants

Our strength: Know-how

Our mastery of lidar technology and all its components enables us to adapt platforms to a wide range of applications.

Fields of application:

  • Indoor/outdoor environmental and industrial surveillance and monitoring

  • Detection of air pollutants over large spaces 

  • Emissions testing

  • Remote leak detection in pipelines and refineries

  • Remote detection of aerosolized biological agents

  • Health and safety


This platform, which is similar to active differential optical absorption spectroscopy (DOAS), uses a variable-spectrum laser source (<1 nm to >50 nm) in the SWIR/MWIR band. Light is produced by nonlinear generation in a periodically poled crystal in parametric amplification mode. The detection system combines both a spectrometer and a range-gated imager (with a temporal resolution of 10 ns or more) to deliver a spatial resolution of several meters along the laser beam. The system uses an HgCdTe avalanche photodiode (MCT-APD) imager. It can also measure differential absorption by scanning the wavelength of one or more lasers injected in the periodically poled crystal. The system was designed in response to demand for a means of detecting natural gas (methane) pipeline leaks from an aircraft flying at high speed and at a higher altitude than can be handled by other platforms presently on the market.

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