Static Fourier transform mid-infrared spectrometer with increased spectral resolution using a stepped mirror

Due to their high light throughput, static single-mirror Fourier transform spectrometers (sSMFTS) are well suited for spectral analysis in the mid-infrared range, and at the same time feature a more robust and compact design than conventional scanning instruments. One major drawback, however, is the comparably low spectral resolution, which is mainly limited by the number of detector pixels. Therefore, in this article, we propose a cost-effective design that almost doubles the spectral resolution of an sSMFTS by integrating a stepped mirror in one of the interferometer arms. The calibration process is described and a proof of principle is given by measuring a CO2 laser. The design works in a spectral range from about 2800 cm⁻¹ to 600 cm⁻¹ at a spectral resolution of 7 cm⁻¹ and offers the potential to improve resolution even further.