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

We present a novel mid-infrared spectrometer that operates within the spectral range of 3– $5~\mu $ 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 $2.49\times 10^{{8}}$ cm $\surd $ 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– $5~\mu $ m mid-infrared region.