Fourier Transform Spectrometer (FTS)

Our laboratory possesses several home-built Fourier-transform spectrometers (FTS) [1]. The FTS is an interferometric spectrometer, which is usually built based on a Michelson interferometer with (at least) one moving mirror and a broadband light source. The moving mirror provides the interference between the two beams at different optical path differences (OPDs). This interference pattern (widely known as “interferogram”) is recorded by a photodetector, and the Fourier transform of the interferogram yields the optical spectrum. In absorption spectroscopy, the sample is placed in the path of the broadband beam, usually before the spectrometer. The transmitted light is sent to the spectrometer, and the absorption features of the sample will be visible in the measured optical spectrum. Advantages of the FTS include the broad spectral coverage and high spectral resolution. In contrast to spectrometers based on dispersive elements (i.e., grating spectrometers), the spectral coverage does not depend on the geometry of the spectrometer but is only dictated by the transparency window of the transmissive elements and the spectral response of the detector. The broad spectral coverage of our FTSs therefore makes them highly suitable for applications in combination with our ultra-broadband supercontinuum sources [2]. The resolution is dictated by the OPD of the instrument and can easily be adjusted to accommodate the system’s application [1].

Set-up of a Fourier Tansform Spectrometer.
References
  1. M. A. Abbas, K. E. Jahromi, M. Nematollahi, R. Krebbers, N. Liu, G. Woyessa, O. Bang, L. Huot, F. J. M. Harren, and A. Khodabakhsh, "Fourier transform spectrometer based on high-repetition-rate mid-infrared supercontinuum sources for trace gas detection," Opt. Express 29(14), 22315–22330 (2021).
  2. R. Krebbers, K. Van Kempen, F. J. M. Harren, S. Vasilyev, I. F. Peterse, S. Lücker, A. Khodabakhsh, and S. M. Cristescu, "Ultra-broadband spectroscopy using a 2–11.5 µm IDFG-based supercontinuum source," Opt. Express 32(8), 14506–14520 (2024).