7 March 2005 Microcavity light emitters and microbolometer detectors for gas monitoring in the 2-5 μm range
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Abstract
A sensor based on selective optical absorption allows monitoring of hazardous engine exhaust emissions such as gaseous hydrocarbons and carbon monoxide. The IR components presented here offer the potential to develop a compact, fast and selective sensor reaching the technical and cost requirements for on-board automotive applications. Optical gas monitoring requires light sources above 3 μm since most of the gas species have their fundamental absorption peaks between 3 and 6 μm. We report here on resonant microcavity light sources emitting at room temperature between 3 and 5 μm. The emitter combines a CdxHg1-xTe light emitting heterostructure and two dielectric multilayered mirrors. It is optically pumped by a commercial III-V laser diode. The principle of the resonant microcavity emitter allows tailoring of the emission wavelength and the line width to fit the absorption band of a specific gas, ensuring a very good selectivity between species. Moreover, this kind of emitter allows fast modulation enabling high detectivity and short response time. We report performances of light sources in the range 3 - 5 μm allowing the detection of hydrocarbons and carbon monoxide. Association of emitters peaking at different characteristic wavelengths with a single broad band detector allows designing of an optical sensor for several gas species. Sensitivity and time response issues have been characterized: detection of less than 50 ppm of CH4 on a 15 cm path has been demonstrated on synthetic gas; analysis of exhaust gases from a vehicle has allowed the resolution of a cylinder time. This optical sensor offers the potential of various on-board automotive applications.
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Eric Mottin, Eric Mottin, Philippe Ballet, Philippe Ballet, Francois Levy, Francois Levy, L. Mathieu, L. Mathieu, Jean Louis Ouvrier-Buffet, Jean Louis Ouvrier-Buffet, J. Rothman, J. Rothman, Jean Jacques Yon, Jean Jacques Yon, Emmanuel Hadji, Emmanuel Hadji, Emmanuel Picard, Emmanuel Picard, } "Microcavity light emitters and microbolometer detectors for gas monitoring in the 2-5 μm range", Proc. SPIE 5739, Light-Emitting Diodes: Research, Manufacturing, and Applications IX, (7 March 2005); doi: 10.1117/12.588584; https://doi.org/10.1117/12.588584
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