High-resolution dual-band triple-grating spectrometer for atmospheric CO₂ detection

The detection of atmospheric carbon dioxide concentrations typically occurs within the near-infrared spectral band. To achieve high-precision measurements, it is essential not only to maintain high spectral resolution but also to capture spectral information across multiple wavelength ranges. Therefore, we propose a novel, to our knowledge, optical design for a high-resolution dual-band triple-grating spectrometer (DTGS). The design strategy is centered on fully utilizing the grating through simultaneous ±1<i>s</i><i>t</i>-order diffraction, enabling high-resolution acquisition of dual-band spectral information while enhancing system integration. We performed theoretical derivations and simulation validations for the initial structure of the DTGS system. The simulation results indicate that the DTGS system achieves high-resolution detection (0.072-0.075 nm spectral resolution) in near-infrared dual-band <i>C</i><i>O</i>₂ weak absorption spectra (1.556-1.576µ<i>m</i> and 1.578-1.598µ<i>m</i>) through a grating configuration of one 555 lines/mm and two 1100 lines/mm, overcoming the spectral resolution constraints of traditional optical systems in wide-band measurements.