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Lidar linéaire et non linéaire dans l'infrarouge moyen

Abstract : The aerosols are an essential component of the urban pollution and of physico-chemistry of the atmosphere. It's of the first interest to dispose of three-dimensions concentration maps with lidar method. An original method, with one wavelength, has been developed. It's based on the impacting and study of filters and their composition. In particular, the distribution is bimodal with one mode at 20 nm and the other one around 1 μm. With our lidar, we have measured the aerosol concentration, the evolution and the stratification of the boundary layer. But, this method is heavy because of the filters study, and use as a strong hypothesis that the atmsophere is homogeneous vertically.
To distinguish between the modes of the distribution and obtain an “all-optical” diagnostic, we have extend in the infrared, more sensitive to micrometer sized aerosols, the existing UV lidar system, more sensitive to the small sizes.
This extension is based on optical parametric oscillators (OPO). The different crystals, capable of producing efficiently mid-infrared wavelengths, have been tested. These crystals are the KTiOPO4 (KTP), the KTiAsO4 (KTA) and the KNbO3. After that, one of these OPO has been implemented in our lidar system. Preliminary infrared lidar concentration measurements have been obtained for water droplets during a haze episode.
Concurrently to the preceding linear lidar systems, a non-linear lidar project (Teramobile project) is born. A white light source, due to generated filaments in the air during terawatt laser beam propagation, is used to do multispectral aerosol lidar. With this source, from UV to mid-IR, aerosol concentration measurements will be possible without any a priori hypothesis, contrary to the preceding methods.
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Submitted on : Wednesday, June 17, 2009 - 4:32:43 PM
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Didier Mondelain. Lidar linéaire et non linéaire dans l'infrarouge moyen. Physique [physics]. Université Claude Bernard - Lyon I, 2001. Français. ⟨tel-00396346⟩

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