Laboratory implementation of Fourier transform infrared (FTIR) spectrograph using a super-continuum laser

Abstract

Fourier Transform infrared (FTIR) spectroscopy is a technique to indirectly measure the spectrum of electromagnetic wave over a broad range. The vibrational response signature will be revealed through the absorption spectrum. The super-continuum laser is the appropriate option for using as a light source of FTIR because of its broad spectral bandwidth and high spatial coherence, which could expand the observable region. In this work, a custom design of laboratory prototype of FTIR system using a super-continuum laser with a wavelength in the range of 1500 – 2 400 nm (6667 – 4167 cm−1) is presented. The system was designed to have a combination of monochromatic and broadband interferometers in a free space Michelson interferometer configuration. An interferogram of a monochromatic laser at 532 nm (18 797 cm−1) was used to correct the phase distortion in the interferogram of the broadband light source. The location of peaks and valleys of the monochromatic interferogram were used to resample the broadband interference signal. The resulting spectrum was analyzed and then compared to the theoretical spectrum for further performance improvements.