From Event: SPIE Commercial + Scientific Sensing and Imaging, 2017
Prevision of climate change is presently one of the main research goals. In order to improve the accuracy of current climate models, it is necessary to better characterize the main greenhouse gases concentration and fluxes (CO2, CH4, and water vapor) at a global scale. For this purpose one promising solution is the space-borne integrated path differential absorption lidar (IP-DIAL) technique, which is currently investigated by space agencies in the preparation of future missions such as MERLIN (CNES-DLR) for methane, or ASCENDS (NASA) for carbon dioxide. One of the challenges for these missions is to have high energy laser sources which can emit specific wavelength to address the species of interest. At ONERA, a high energy transmitter based on a broadly tunable parametric source has been developed in the 2 μm spectral region to address the main greenhouse gases absorption lines that are well-suited for space application1. This source has been recently implemented on the R30 CO2 absorption line at 2051 nm for ground-based range resolved measurements in the atmosphere. In our set-up the source emits 10 mJ pulses at a 30 Hz repetition rate. The backscattered light from aerosols is collected with a Newton telescope and a direct detection scheme based on an InGaAs photodiode. CO2 concentration has been estimated with a precision better than 25 ppm for a 200-meter spatial resolution in the 100-500 m range and a 10 minutes acquisition time.
Erwan Cadiou, Jean-Baptiste Dherbecourt, Guillaume Gorju, Jean-Michel Melkonian, Antoine Godard, Jacques Pelon, and Myriam Raybaut, "Direct detection range resolved carbon dioxide differential absorption lidar measurements in the 2 µm range," Proc. SPIE 10215, Advanced Environmental, Chemical, and Biological Sensing Technologies XIV, 102150L (Presented at SPIE Commercial + Scientific Sensing and Imaging: April 10, 2017; Published: 3 May 2017); https://doi.org/10.1117/12.2262497.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon