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Proceedings Paper

Fabry-Pérot-based thin film structure used as IR-emitter of an NDIR gas sensor: ray tracing simulations and measurements
Author(s): Johann Mayrwöger; Christian Mitterer; Wolfgang Reichl; Christian Krutzler; Bernhard Jakoby
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Paper Abstract

Non-dispersive infrared (NDIR) gas sensors make use of the specific infrared absorption of particular gas molecules in order to measure their distinctive gas concentration. The main parts of such a NDIR gas sensor are: an IR-emitter, a chamber containing the sample-gas, and an IR-detector with a filter for the characteristic absorption wavelength. The effectiveness of the IR-source for the total system is characterized by its temperature and the emissivity (i.e., the difference to blackbody radiation) of the device surface. Due to the fact that conventional metal surfaces provide a rather low emissivity, their emitting temperature must be set very high to generate sufficient IR-radiation for this kind of sensors. We developed an IR-source consisting of a stack of thin films with a much higher emissivity. Its main part is a combination of two mirrors and a dielectric layer which represent a Fabry-Perot structure. The obtained emission of the Fabry-Perot structure and the consequences for the performance of the whole NDIR gas sensor system were simulated with the enhanced transmittance matrix approach and a 3D ray tracing model. As an example, CO2 was considered as sample gas where the major characteristic absorption occur around 4.26 μm. The theoretical results are validated by comparing them to experiments obtained with prototype devices.

Paper Details

Date Published: 5 May 2011
PDF: 10 pages
Proc. SPIE 8066, Smart Sensors, Actuators, and MEMS V, 80660K (5 May 2011); doi: 10.1117/12.886741
Show Author Affiliations
Johann Mayrwöger, Johannes Kepler Univ. Linz (Austria)
Christian Mitterer, Univ. of Leoben (Austria)
Wolfgang Reichl, E+E Elektronik (Austria)
Christian Krutzler, Integrated Microsystems Austria (Austria)
Bernhard Jakoby, Johannes Kepler Univ. Linz (Austria)

Published in SPIE Proceedings Vol. 8066:
Smart Sensors, Actuators, and MEMS V
Ulrich Schmid; José Luis Sánchez-Rojas; Monika Leester-Schaedel, Editor(s)

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