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Proceedings Paper

Resonant microcavity light emitters for onboard exhaust emissions IR sensor
Author(s): Francois Levy; Emmanuel Picard; Johan Rothmann; Eric Mottin; Emmanuel Hadji; Joel Duhr
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Paper 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 3μm 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 5μm. 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 3-5μm 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 50ppm of CH4 on a 15cm path has been demonstrated on synthetic gas; analysis of exhaust gases from a vehicle has allowed cylinder to cylinder resolution. This optical sensor offers the potential of various on-board automotive applications.

Paper Details

Date Published: 16 February 2005
PDF: 12 pages
Proc. SPIE 5663, Photonics in the Automobile, (16 February 2005); doi: 10.1117/12.597602
Show Author Affiliations
Francois Levy, CEA-LETI (France)
Emmanuel Picard, CEA-DSM (France)
Johan Rothmann, CEA-LETI (France)
Eric Mottin, CEA-LETI (France)
Emmanuel Hadji, CEA-DSM (France)
Joel Duhr, Delphi Technical Ctr. (Luxembourg)

Published in SPIE Proceedings Vol. 5663:
Photonics in the Automobile
Thomas P. Pearsall, Editor(s)

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