Design of a static Fourier transform spectrometer
for the 8-12 μm infrared region

Filip Łabaj

supervisor: Ryszard Piramidowicz

We present results of ongoing development on a mid-infrared, static Fourier transform spectrometer (sFTS) based on the triangular Sagnac interferometer configuration and designed to work in the 8-12 μm spectral range. This enables access to spectral data from the so-called “fingerprint region” and in effect – to a plethora of potential analytes.

Preliminary numerical simulations were performed using ray-tracing software in order to select a suitable interferometer architecture. Theoretical parameters and detection limits of the setup were calculated in order to confirm its suitability for spectrometric applications.

The designed setup was then constructed and experimentally tested, first by analyzing well-defined, quasi-monochromatic light sources and afterwards – by measuring spectral transmission characteristics of thin samples and spectral filters illuminated by a broadband thermal source.

Two approaches to interferogram sampling were compared during the experimental phase – a high resolution, two-dimensional microbolometer array and a single-element detector scanning setup.

Interferograms measured in the system are processed in several steps, which include denoising and demodulation. Spectral data is then retrieved using the fast Fourier transform (FFT) algorithm.

An outline for future work on the system is presented, as well as potential applications of the setup.