Enhancing static modulated Fourier-transform spectrometer performance through a stepped mirror structure and...

While a static modulated Fourier transform spectrometer offers advantages such as rapid data acquisition and vibration immunity to over a dynamic modulated Fourier transform spectrometer, addressing the trade-off between spectral resolution and signal-to-noise ratio remains a significant challenge. This paper presents an approach to simultaneously enhance both spectral resolution and signal-to-noise ratio by combining two different interferograms. A detailed procedure, involving an application based on spectral reconstruction, is outlined, and the effectiveness of the proposed approach is experimentally verified.The spectrometer consists of a modified Sagnac interferometer with stepped mirrors. In this experiment, interferograms were acquired at mirror displacements of 1 mm and 14 mm using a source with a spectral width of 124.6 cm^-1 and center wavenumber of 15,259.7 cm^-1. The proposed approach extends the maximum optical path difference of the short mirror displacement, by incorporating information obtained at a long mirror displacement. The proposed method significantly improved the spectral resolution from 272.5 cm^-1 to 17.6 cm^-1. This spectral resolution is only 0.2 cm^-1 lower than that achieved at a 14 mm mirror displacement. Furthermore, the spectral width obtained via the proposed approach was 122.4 cm^-1, yielding an R² value of 0.95, when compared to a monochromator reference, a 0.20 improvement over the 14 mm mirror displacement results. Regarding the signal-to-noise ratio, the values are 5.67 and 2.07 for the 1 mm and 14 mm mirror displacements, respectively, while the proposed approach achieved a signal-to-noise ratio of 15.47. This methodology demonstrates the potential of static modulated Fourier transform spectrometer for high performance applications in low signal-to-noise conditions, such as Raman scattering detection and remote-sensing.