Infrared optical sensor for CO2 detection

Among the measures to reduce CO2 emissions, capture and geological storage holds out promise for the future in the fight against climate change. The aim of this project is to develop a remote optical sensor working in the mid-infrared range which will be able to detect and monitor carbon dioxide gas. Thus, chalcogenide glasses, transmitting light in the 1-6 μm range, are matchless materials. The first of our optical device is based on the use of two GeSe4 chalcogenide optical fibers, connected to an FTIR spectrometer and where CO2 gas can flow freely through a 4 mm-spacing between fibers. Such sensor system is fully reversible and the sensitivity threshold is about 0.5 vol.%. Fiber Evanescent Wave Spectroscopy technology was also studied using a microstructured chalcogenide fiber and first tests led at 4.2 μm have provided very promising results. Finally, in order to explore the potentiality of integrated optical structures for microsensor, sulphide or selenide Ge25Sb10S(Se)65 rib waveguide were deposited on Si/SiO2 wafer substrates, using pulsed laser deposition and RF magnetron sputtering deposition methods. The final aim of this study is to develop a rib waveguide adapted for middle-IR including an Y-splitter with a reference beam and sensor beam targeting an accurate CO2 detection.