CO2 Monitoring Spectrometer with 640×512 Pixel SWIR InGaAs Focal Plane Array

This paper introduces a prototype grating spectrometer measuring atmospheric column carbon dioxide (CO₂) with a 640 × 512 pixel indium gallium arsenide (InGaAs) focal plane array (FPA). The spectrometer achieves the spectral resolutions of 0.1 nm at 1.61 μm CO₂ band meets the measurement requirement. The structure of the spectrometer including optics and electronics has been described in this paper. The spectrometer features a relatively fast optics, f/1.8, which benefits the sensitivity, and combines a fine slit with a large planar reflective diffraction grating. The performance of the optical design is presented to demonstrate the optical system meets the requirements for spectral resolution and sensitivity. The 640 × 512 InGaAs FPA with a low noise acquisition system serves to provide low noise spectral signals. The 640 × 512 InGaAs FPA, 25 μm pixel size, is sensitive to 0.9 μm-to-1.7μm short wave infrared (SWIR) band and features a 298 K temperature detectivity, D*, greater than 5 × 10¹² cm^-1√Hz/W.