Low-Cost Computational Mid-Infrared Spectrometry for Atmospheric Gas Sensing With Wavelength-Selective Microbolometer Arrays

• Published in: IEEE sensors journal Vol. 24; no. 24; pp. 40240 - 40250
• Main Authors: Rabiul Hasan, Md, Nikeghbal, Amirali, Tran, Steven, Deshpande, Adwait, Karkhanis, Mohit U., Pourshaban, Erfan, Banerjee, Aishwaryadev, Noh, Seungbeom, Kim, Hanseup, Mastrangelo, Carlos H.
• Format: Journal Article
• Language: English
• Published: New York IEEE 15.12.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Absorption; Arrays; CO₂ sensor; Detectors; Filters; gas sensor; Gas sensors; Infrared absorption; Infrared spectra; Infrared spectrometers; Infrared spectroscopy; micro-electro-mechanical system (MEMS); microbolometer; mid-infrared spectroscopy; Narrowband; Optical filters; Packaging; Polysilicon; Regularization; Regularization methods; Sensors; Silicon; Silicon nitride; Spectral sensitivity
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2024.3427689

We present a novel mid-infrared spectrometer that operates within the spectral range of 3-<inline-formula> <tex-math notation="LaTeX">5~\mu </tex-math></inline-formula>m range for atmospheric gas measurements without the assistance of a vacuum. This spectrometer utilizes an array of silicon microbolometers, each with a different overlapping broad spectral response. Each microbolometer features a suspended silicon nitride platform, a polysilicon thermistor, and an infrared absorber layer all positioned above platinum mirror. By utilizing this membrane-based microbolometer, the device achieved a tenfold increase in response when compared to regular substrate-based microbolometer at an average of 45 000 V/W responsivity, allowing for a heightened detectivity of <inline-formula> <tex-math notation="LaTeX">2.49\times 10^{{8}} </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">\surd </tex-math></inline-formula>Hz/W. The spectrum of the incoming radiation is obtained computationally from the bolometer array collective response via regularization methods, thus eliminating the need for costly narrowband IR filters. Additionally, the device's gas detection capability was validated with CO2 and CO gas testing, both of which exhibit significant absorption within the expected 3-<inline-formula> <tex-math notation="LaTeX">5~\mu </tex-math></inline-formula>m mid-infrared region.