7 March 2005 Microcavity light emitters and microbolometer detectors for gas monitoring in the 2-5 μm range
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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.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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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