Enhancement of Spectral Resolution in a Static Modulated Fourier-Transform Spectrometer with Stepped Mirrors

A static modulated Fourier transform spectrometer has advantages such as rapid evaluation and immunity to vibration over a dynamic modulated Fourier transform spectrometer. However, addressing the trade-off between spectral resolution and signal-to-noise ratio remains a challenge. In this paper, an approach to enhance both spectral resolution and signal-to-noise ratio is introduced, and its effectiveness is verified through the theoretical analysis. The spectrometer is comprised of a modified Sagnac interferometer with stepped mirrors. Enhancement is achieved by combining two different interferograms. Its detailed procedure, involving an application based on the spectral reconstruction, is outlined in this study. By combining interferograms acquired with mirror displacements of 1 mm and 5 mm, the spectral width is 128.3 cm^−1. It is 66% narrower than the spectral width at 1 mm mirror displacement and 0.3% broader than at 5mm mirror displacement. The standard deviation representing signal-to-noise ratio is 2034. It is 216% improvement compared to the 1 mm mirror displacement, and 485% improvement compared to the 5 mm mirror displacement. This approaching method also shows the potential of the static modulated Fourier transform spectrometer for applications in low signal-to-noise conditions such as Raman scattering detection and remote-sensing.