Abstract
A miniaturized methane (CH(4)) sensor based on nondispersive infrared absorption is realized in MEMS technology. A high level of functional integration is achieved by using the resonance cavity of a linear variable optical filter (LVOF) also as a gas absorption cell. For effective detection of methane at λ = 3.39 µm, an absorption path length of at least 5 mm is required. Miniaturization therefore necessitates the use of highly reflective mirrors and operation at the 15th-order mode with a resonator cavity length of 25.4 µm. The conventional description of the LVOF in terms of the Fabry-Perot resonator is inadequate for analyzing the optical performance at such demanding boundary conditions. We demonstrate that an approach employing the Fizeau resonator is more appropriate. Furthermore, the design and fabrication in a CMOS-compatible microfabrication technology are described and operation as a methane sensor is demonstrated.
Highlights
Optical microelectromechanical systems (MEMS) technology has enabled the design and fabrication of various types of microspectrometers operating at different parts of the spectrum [1,2]
The spectral scans at 3.22 μm, 3.27 μm and 3.39 μm confirm that the linear variable optical filter (LVOF) integrated with a gas cell could serve as a chip-level microspectrometer that is capable of distinguishing methane from higher hydrocarbons when combined with a broadband light source and a detector array
It was shown that an LVOF with highly reflective mirrors that operates at a high order must be designed using the Fizeau approach, where the nonparallelism of the mirrors is taken into account, rather than treating it in the conventional approach; as an array of FP filters
Summary
Optical microelectromechanical systems (MEMS) technology has enabled the design and fabrication of various types of microspectrometers operating at different parts of the spectrum [1,2]. In this work we achieved a significant miniaturization of the gas IR absorption spectrometer by functional integration of the sample cell with an optical filter as shown in Fig. 2(b) while ensuring a sufficient absorption for practical measurements. Using the resonance cavity of an LVOF as a gas cell is a promising new concept for high reliability, wideband operation and a significant reduction in the size of MEMS-based absorption spectrometers.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
