CO 2 Detection Using Microstructured Chalcogenide Fibers

In this work, detection in the mid-infrared (mid-IR) of carbon dioxide, so called "greenhouse" gas, using Fiber Evanescent Wave Spectroscopy (FEWS) technique is investigated. Since each pollutant gas shows a characteristic optical absorption spectrum in the mid-infrared, it is possible to detect selectively and quantitatively the presence of gases in a given environment by analysing mid-IR spectra. The main infrared signature of carbon dioxide gas consist in a double absorption peak located at 4.26 mu m. Chalcogenide optical fibres, transmitting light in the 1-6 mu m range, are well-adapted for CO2 analysis. Thus, tapered and microstructured chalcogenide fibers have especially been designed for CO2 detection. They present low optical losses in the spectral region of the CO2 absorption band. The fabrication of tapered and microstructured fibers is reported. Then, using a tapered fiber the detection limit Of CO2 is around 20 vol.%. On the other hand, for the first time to our knowledge, the detection of gas in the mid-infrared is demonstrated with a chalcogenide microstructured fiber.