Compact gas cell integrated with a linear variable optical filter
N.P. Ayerden (TU Delft - Electronic Instrumentation)
G. de Graaf (TU Delft - Electronic Instrumentation)
Reinoud Wolffenbuttel (TU Delft - Electronic Instrumentation)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
A miniaturized methane (CH4) sensor based on nondispersiveinfrared absorption is realized in MEMS technology. A high level offunctional integration is achieved by using the resonance cavity of a linearvariable optical filter (LVOF) also as a gas absorption cell. For effectivedetection of methane at λ = 3.39 µm, an absorption path length of at least 5mm is required. Miniaturization therefore necessitates the use of highlyreflective mirrors and operation at the 15th-order mode with a resonatorcavity length of 25.4 µm. The conventional description of the LVOF interms of the Fabry-Perot resonator is inadequate for analyzing the opticalperformance at such demanding boundary conditions. We demonstrate thatan approach employing the Fizeau resonator is more appropriate.Furthermore, the design and fabrication in a CMOS-compatiblemicrofabrication technolog